Matlab editor displays overlay

Both the editor and the command window sometimes show an overlay of some garbage. It looks like some screengrab takes place at whatever place I click and then this image gets pasted in the editor/variable/command window. Scrolling has the effect of smearing out everything. See images. The garbage is removed if I click some window other than Matlab. The garbage is sometimes removed if I click some other part of Matlab. The issue usually occurs when viewing large files (20000+ lines)

Matlab is still operational, every command still works.

I'm using Matlab R2015b x64 in Linux Mint 17.3 Cinnamon x64

Matlab is using SOFTWARE OPENGL rendering.

I am not out of memory.

It doesn't matter if I start Matlab from terminal or menu, with or without -desktop option, ...

I have no idea what to try next. Please advice.