Thanks for that, I suspect you may have hit the nail on the head, certainly sounds about right.

it's quite random but not too frequent, happened again today while tabbing out to snap a Gyazo.

So I quickly dragged my whole FFXIV window over to 2nd monitor and back and it restored mouse function again ... at least that seems to fix the issue repeatedly when it occurs.

Sadly it sounds like one of those bugs that's living in the crossover between MacOS Catalina, Wine and FFXIV so heaven only knows if/when it'll resolve.

Thanks for the advice