UI elements flickering

I have a problem that started recently, is really difficult to reproduce, some UI graphics start to flick or disappear. QA could reproduce the issue a few times after hours of trying, and we have reports of some users.

I have a scene with a Screen space canvas with multiple nested canvases. tried adding canvases to content that constantly changes for reducing graphic and layout rebuilds, now I have reports of only the content on those canvases flickering.
Since I can’t reproduce it, is really hard to narrow the problem
I am using unity 2019.3.10f1 and only have reported on android.
Any suggestion?
Thanks

Disabling multithreaded rendering setting fixed the issue.