Thank you for the report! I can't say for sure what the issue is, though my understanding is that the web builds use a different version of Python and potentially a slightly different renderer. I did quite a lot of fiddling to get the shaders to work with both ANGLE2 and GL2, and it wouldn't really surprise me that if a slightly different renderer is used for web that it has its own idiosyncrasies. I will put it down on my list when I have a chance to look at it!