SDL MultiTerm 2019 - not recognizing existing terms in Editor, but aware that terms exist

Dear All,

I have the latest version of MultiTerm installed: SDL MultiTerm 2019 -, but the problem described below has been around forever.

I have noticed time and again that MultiTerm does not recognize terms from the termbase (about which my memory serves me better), but when asked to add the term suddenly tells me that the term already exists:

So, the term exists and Trados knows it, but the term is not recognized in the source segment and there is no red bracket above it.

Any ideas?

Best regards,