I was quantizing a drum track and sometimes it erased the notes that I selected and quantized. It was pretty rare, but I saved a file that does it every time right at beat 1 of bar 66. There 2 notes in the bass clef - C and A and one note in the treble clef - E. When I select all 3 notes, the lower 2 notes disappear and the upper one remains is is correctly quantized.

I've tried quantizing to 1/4 1/8 1/16 with the same results. My original track has a drum map, so I created a new midi track with no drum map and copied the data to it and got the same results in that track also. I looked at the event list and see nothing unusual. It also does this in the piano roll view.

I uploaded the CWP file named QUANTIZE ERASES.cwp to this link below. It's only 1 midi track.
https://onedrive.live.com...d=c256e2dae26b22a5!105

Please try this and see if you get the same result, before I turn in a bug report.

Yes, the notes were being deleted initially.
 
Bounce the whole track to one contiguous clip and the Quantize works.
 
I don't know why this is happening but the bounce cures it

Quantize never does what it supposed to, only making everything worse. I gave up using it many years ago.

UPDATE: OK, I opened your file and quantized the Superior Drummer track.  Quantizing at 1/16th worked fine.  Quantizing at 1/8 put notes under each other because two 16ths got moved to the same 1/8 slot.  So, quantizing at 1/8 made it appear notes were disappearing, but they were actually just stacked on top of each other.
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Is the quantization putting two notes on top of each other so it seems one disappeared?
 
For the record, I quantize pretty much everything.

vladasyn
Quantize never does what it supposed to, only making everything worse. I gave up using it many years ago.

Not sure what you mean. If you can describe the problem, there's probably a solution. 

konradh
UPDATE: OK, I opened your file and quantized the Superior Drummer track.  Quantizing at 1/16th worked fine.  Quantizing at 1/8 put notes under each other because two 16ths got moved to the same 1/8 slot.  So, quantizing at 1/8 made it appear notes were disappearing, but they were actually just stacked on top of each other.
***
Is the quantization putting two notes on top of each other so it seems one disappeared?
 
For the record, I quantize pretty much everything.

Thanks for your help.
 
The 2nd poster Jonesey was able to reproduce it. This is a pretty rare occurance, so you have to go to bar 66 and in the time ruler only select the notes close to beat 1 bar 66. There are only 3 notes, then choose quantize and see what happens. If you're in the staff view or piano roll view you actually see the notes disappear, they're not stacked. Thanks for trying it, please try it once more.

There's a reason those notes disappear. The underlying clip boundary structure is what causes it. And that's why bouncing fixes it.
 
The clip that holds those two bass clef notes that play "at" measure 66 actually ends at the end of the previous measure. I.e. the only reason those notes show at all is that they start just before the end of the clip. Quantizing them moves them past the end of the clip, so they are now out of the clip, and gone. Moving the clip boundary a little later before quantize allows them to stay after quantize.

There's a related strangeness, though. That clip still had more notes beyond the clip boundary. They show up if you drag the clip boundary far enough. But quantizing with the original clip boundary then dragging the clip boundary shows that some notes beyond the original end are still there, while others have disappeared. Haven't figured out how to predict yet, but don't depend on notes outside a clip boundary being preserved.
 

vladasyn
Quantize never does what it supposed to, only making everything worse. I gave up using it many years ago.

I only quantize drums and percussion. There are a few things you have to do to insure it works without messing things up. ON a drum track look at it in the staff view and if 16th notes are the fastest notes you've played then start at the last bar and if there's a ritard, go back until you get to regular time and look for 16th notes. Sometimes you'll find some that are wrong, in most cases quantizing to 8th notes for that spot will fix the error.
 
I have CAL macros setup where I hit a hot key and it quantizes to 1/4 1/8 1/16 etc. With Superior drummer for some reason the midi notes tend to be very slightly early and sometimes I need to move the whole track back in the piano roll view by selecting all the notes and moving them very slightly to the right. Then there are few or no quantize errors.

Bristol_Jonesey
Yes, the notes were being deleted initially.
 
Bounce the whole track to one contiguous clip and the Quantize works.
 
I don't know why this is happening but the bounce cures it

 
Thanks you have an easy workaround, which I'll use until they fix this. I turned in a bug report and gave them your workaround
 
Thanks for all your help,