Studio 15.2.5.2145. Input model is deselected when adding terms (bug?)

The input model is de-selected when adding new terms (both Add term and Quick add term).

I have been Reviewing 3 files (17k words) and after a few hours, the Input model changes to (No input model) for no apparent reason. Closing and opening the files in the Editor didn't correct the problem but restarting the program did. I'm reporting this just in case this is a bug.