Trivial clip mute issue.

Works as expected here...

Can no longer reproduce either.... Thanks...

Give us the specific steps from a new project (like the steps in the first post) and I'll check it out. Thanks.

Thanks Dave I will look for this edit filter, thought it might be that kind of thing,, You have to bear with me as I still expect things work the way they did in 8.5, I'm still pretty green as far as X behavior goes and I daily run into weird things I don't understand. 
 
The tracks are audio, vocals,guitar and are not continuous having a few punch ins so might involve 4 or more " clips" if that is what they become? I myself have never knowingly changed anything about the actual tracks. But I will admit I often accidentally will hit keys by mistake.
Now I will say all of these started life in 8.5 if that makes a difference.  
 
But what I find is the minute I add automation to a track it becomes stubborn and cannot be highlighted or edited.  
So I have to delete all envelopes and then toggle the R off and the track becomes "normal" again.
Thank goodness I did not spend any time writing the automation and it's easily re done. 
I poked around looking for some clue to what "state" it had become. The new "help" files are obviously only on line but I downloaded the PDF and wade my way though it when bored. I  also have a copy of Scott's Power  for X1 which is easy reading and a great help,   I think everything is still relevant to x3 but I have only made it to page 78. Anyhow if it's like 8.5 it will be a year before I'm doing things correctly. 
The forum is a big part of the learning process for me. Trouble is we don't like to ask a million questions about the stuff that's most likely well covered somewhere in the text. 
 

I have been happily using Sonar/ Cakewalk since 2004,,,an edit filter is a new one to me, just goes to show.. sorry for the hijack Alex,, I figured you wouldn't be too upset.. 

Cactus Music
But what I find is the minute I add automation to a track it becomes stubborn and cannot be highlighted or edited.

Yeah that's totally Edit Filter behavior. I still bump my head on that regularly, partly because the Smart tool is so all-powerful that I expect it to be ready to do anything I want all the time.
 
Adding an automation envelope automatically changes the Edit Filter to that automation type so you can edit it without accidentally moving/editing other objects. The quick way to get back to editing the clip is to Shift+click it. Or you can explicitly change it using the picker in the track header or in the Tools HUD (T or Center/Wheel+click). Shift+click on the envelope (or another envelope), and you're editing the envelope again.