UI Elements disappear when running multiple instances

[ps]

I got some users reporting (all of them are logic users I believe) that when they are running multiple instances of a plug-in of mine - ui elements are disappearing.
From screenshots it looks like panels with aligned text painted on them (preset browser) that go blank but also labels. But also not all of them necessarily.
Has anybody had this case yet? There’s no logic I could find behind it but I def happens and is kinda disturbing.