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ok, we might probably have found the bug.

Not easy to fix though, so don't expect a bugfix soon.

You found it? Great. I logged keyboard typing history but I couldn't find anything strange, but I guess this glitch has something to do with canvas rotation(alt + ctrl + left click) or zoom in and out(alt+right click) + aliased pen tools.This glitch always starts when I use aliased pen and both mouse + keyboard shortcuts.
I don't use mouse to activate those shortcut. I always use pen tablet, so maybe this glitch is caused by pen tablet because those shortcuts are supposed to work not with pen tablet, but with mouse ?

yes, I think we found it.
At least there was a lag bug with the undo stack when it was full.
You might try to increase the undo size in the preferences, the bug should occur later.
It will be fixed in TVPaint Animation 11.

Thank you. I will increase undo size.