Text edit not what it used to be

More recently we have found making simple edits to existing text getting very patchy.
For instance, highlighting a couple of lines of copy - right click to raise the edit menu - selecting the Design tab - change Font Weight... nothing happens. Change to an extreme weight it might change, change it back to the lighter weight and it might revert to the original set weight but not the newly desired weight. There's a lot of 'mights' involved. For some reason it really doesn't always do what is asked.

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