Konrad, I doubt the solution is to buy a new PC. I have found automation to be rock-solid with Sonar, BUT it's VERY easy to have pilot error cause problems. For example I clicked to enter a node in an automation section to raise the level, but didn't remember to enter another node in front of it to "anchor" the existing automation line. So the new node caused a massive level increase.
 
Automation in Sonar is actually quite complex. I like that you can float the cursor along the top of a clip and drag up or down to change an entire envelope, but it took me a while to find that option. I also had to remember to set an initial level, and often, I need to use the Overwrite or Latch modes to maintain the integrity of the automation envelope. I now consider myself a "master of automation," but it has taken me a while to get there...and I'm probably fooling myself anyway! I'm sure there are things I still need to learn.
 
It's frustrating that in your case, I think if I was in your studio looking over your shoulder, we'd narrow down the problem in minutes. Maybe you could do screen captures that illustrate how the automation problems occur?

Craig, Many thanks.  And the automation function may just be caused by a number of user-errors + awkward functions.  I did discover that, for me, Offset works differently depending on whether or not tracks are in folders and whether or not they are Write-enabled.
 
However, I do have many bizarre issues unrelated to automation that no one seems to be able to explain.  I won't re-document them all here, but just to give you a a few examples so you know what I mean:
 
1-Sometimes I open a project and the Ins/Outs on every track are messed up: vocal track In set to Vienna, Ivory track output set to Fantom, external synths set to the wrong V-Studio inputs, MIDI Ins/Outs all wrong, etc.
2-Adding VIs/soft-synths will kill all audio.  I have plenty of memory and CPU in all cases, and the number of VIs varies.  For example, audio may stop in a project with six VIs (even though all the meters show audio in the track and at Master).  Sometimes 13 VIs is OK and 14 kills audio.  The odd thing is that I use the same VIs most of the time: RealGuitar, Kontakt, Ivory, etc.  Sometimes I can solve the problem by freezing a synth.  Sometimes I have to delete one.  After freezing or deleting, I may get audio back by cycling the audio engine.  Sometimes I have to reboot the PC.
3-Performance of large string libraries is terrible even though I have cleaned out disk space, defragged, and added memory.  Although everyone says I should go to SSDs (and I will), other people use Vienna and Hollywod from spinning disks, and many do much more elaborate orchestration than I do.
4-Lots of crashes for odd reasons.  Often, opening the Staff View will freeze/crash Sonar; sometimes it is opening Melodyne; sometimes it is just in the middle of normal editing; etc.
5-Common functions cease to wrok.  Split clips will suddenly stop working.  Often Crtl X/C/V stops working and edits can only be done from menus.  Sometimes Cut/Copy/Paste stop working completely from either short-cuts or menus.  Sometimes paste goes to unpredicable places and the Paste Special box won't allow me to direct it to the correct place.
6-A project will peak at Master.  I replay the track from the start and there are no red peaks (not even close).  Play it another time, and I get red again.  There are no external synths or VIs running with LFO, modulation, etc. that vary signal strength or EQ.
 
Those are just a few to give you an idea of how strange things are. 
 
 

konradh
1-Sometimes I open a project and the Ins/Outs on every track are messed up: vocal track In set to Vienna, Ivory track output set to Fantom, external synths set to the wrong V-Studio inputs, MIDI Ins/Outs all wrong, etc.

 
Do you have more than one audio interface? If there's an internal audio sound chip, have you tried disabling it using Device Manager? It's a long shot, but disabling the internal sound chip can sometimes help with various issues.
 

2-Adding VIs/soft-synths will kill all audio.  I have plenty of memory and CPU in all cases, and the number of VIs varies.  For example, audio may stop in a project with six VIs (even though all the meters show audio in the track and at Master).  Sometimes 13 VIs is OK and 14 kills audio.  The odd thing is that I use the same VIs most of the time: RealGuitar, Kontakt, Ivory, etc.  Sometimes I can solve the problem by freezing a synth.  Sometimes I have to delete one.  After freezing or deleting, I may get audio back by cycling the audio engine.  Sometimes I have to reboot the PC.

 
Do you have the Kontakt 5.3 update? It solved a bunch of weird audio engine problems I had in projects that included Kontakt. These only showed up with large track counts. Now it's running super-smooth regardless of track count.
 

3-Performance of large string libraries is terrible even though I have cleaned out disk space, defragged, and added memory.  Although everyone says I should go to SSDs (and I will), other people use Vienna and Hollywood from spinning disks, and many do much more elaborate orchestration than I do.

 
There could be lots of reasons for this...I don't have Vienna or Hollywood installed, so can't offer any specific tips. But do remember that even if samples stream from disk, they still need RAM to store the attacks. Sometimes you have to tell a program how much RAM to allocate. If you added RAM, there's no guarantee a program recognizes it and takes advantage of it...although it might...
 

4-Lots of crashes for odd reasons.  Often, opening the Staff View will freeze/crash Sonar; sometimes it is opening Melodyne; sometimes it is just in the middle of normal editing; etc.

 
Have you run memtest on your memory and chkdisk on your hard drives? Internal RAM is not flawless, does get hot, and can fail partially rather than doing a complete fail. I used to have incredibly strange, weird, unpredictable crashes and performances issues with a Mac. I did updates, repaired permissions, check the hard drive, tried uninstalling specific programs...everything. I even used a program to check the RAM, and it checked out okay. BUT...the program used the OS to check RAM. Only when I ran a RAM test from within the Mac's Command Line Interface (yes, it has one) was the problem identified as a bad RAM stick. Once I replaced that, my problems disappeared.
 

5-Common functions cease to work.  Split clips will suddenly stop working.  Often Crtl X/C/V stops working and edits can only be done from menus.  Sometimes Cut/Copy/Paste stop working completely from either short-cuts or menus.  Sometimes paste goes to unpredictable places and the Paste Special box won't allow me to direct it to the correct place.

 
Humor me and try a different keyboard. Switches in most modern keyboard fail closed, not open. If a key is failing and closes periodically, you'll get all kinds of craziness. Why do I know? This has happened to me!
 

6-A project will peak at Master.  I replay the track from the start and there are no red peaks (not even close).  Play it another time, and I get red again.  There are no external synths or VIs running with LFO, modulation, etc. that vary signal strength or EQ.

 
That is clearly due to interference from alien lifeforms. Please check whether a UFO is hovering over your house.

Craig, Thank you for taking time to reply so completely.
 
Starting with your last point, as the best example of a human being's physical form and mental capabilities, it would not be surprising that I would be the subject of alien studies.
 
I am on Kontakt 5.2.1.6xxx so going to 5.3 is worth a try.
 
I only have one audio interface active.  I believe Sweetwater would have disabled the internal sound chip in the Creation Station, but that is worth checking.
 
I believe the memory and disk are OK, but I will recheck.
 
About the keyboard, your observation is excellent and good to keep in mind.  In this case, I have had these issues since Day1 and have changed keyboards a few times.  Also, when Split stops working, it stops working from the menus and icons.
 
Thanks again!