No obvious sources of problems there, unfortunately. Have you noticed any particular situation that tends to lead to this happening? Is it always the first time you open the reader on a particular day, for example, or always after you've exited Pleco or rotated your screen or opened some specific other app or switched into split screen mode or switched into dark mode, anything like that?
We'll see if we can manage to reproduce this here, but otherwise we just have to wait + hope enough people report similar problems that we can triangulate it.