Question: Icons dissapearing

What might be the reason for the GUI loosing icons during a session? It looks like this

Mouse over let the icons reappear.

This problem is not new to me and only happens from time to tim

I have not found out under what conditions this happens.
The only thing I can say is that I didn't see it after restarting Maple.
And: Only the icons on the left-most disappear.

Everything under Windows 10

Has anyone seen the same thing?

Any idea how to fix this?

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