bena Thank you for sending us the Spine project that can reproduce the problem! I have confirmed that I can reproduce this issue with Spine 4.0 and 4.1 as you described, but not with the latest 4.2, so I assume that this issue has been fixed in 4.2. Please upgrade to 4.2 to resolve this issue, as 4.0 is a version that we have already finished updating and we cannot make any changes to this version.
As a way to fix this popping behavior in 4.0, there seems to be a problem with the default Bezier curve, and moving the handle even slightly seems to solve the problem. As far as I have tried, changing the angle or length of the handle just slightly quickly fixed the popping behavior, which may be easier than repeatedly pressing the Bezier curve button.
