Strange screen appearance

I observe occasionally following screen.

Has someone else observe a similar screen?

Does someone know the route cause?

I filed a bug report to allow others to add comments and thus provide more information for our devs to solve he bug. fdo#65114

I am using LibO Version 3.6.6.2 (Build ID: f969faf) on XPPrpf/SP3

fdo#65114 · Status: RESOLVED INVALID

Additional note - If you see such a screen, I recommend to immediately save your file with ctrl+s. In my case - until now - I could save my file always .