Can you post some screen shots? When you say "dynamic object," I'm assuming you mean Smart Object? How are you transforming it - are you right clicking and selecting an option such as distort, skew, etc? Are you holding any modifier keys such as ctrl/cmd?
Thank you for your answer.
It's a smart object, yes (tested with vector object or simply image object, and without being a smart object just a pixel element).
This bug happens when right cliking for a transform, or by choosing a transformation in the menu, and only if the object has already been transformed one time. it's a second transformation that makes the bug happening.
Holding a modifier key or not, doesn't make it happening more often or less.
by the way, working from a new file has made this bug disappear. the original file must have been corrupted, but i don't know how.
Sometimes odd things happen to just one file. I've had that happen a lot, where I think I found a bug, but it's only in one file.