When I first ran S&R this morning (my time) the add-in went into a long think (tens of seconds), there was nothing to indicate it was 'thinking' - i.e. no spinning wheel pointer etc. I was about to exit Word via Alt/space+C when my first 'Process tables' message 'popped'. I let that one do its thing (they are auto corrections), and then my second 'Process tables' message 'popped', it requires intervention.
My guess is that the 'long think' was probably the process when it adds the Whole Word column to my replace rules document (
which is quite large) and transforms that into the ePUBToolsSRRules.xml file. And, yesterday I just didn't wait long enough and did the Alt/space+C exit.
Since then of course there are no noticeable delays - S&R is now lickety-split slick
I'm not inclined to restore my replace rules back to 1.12.2 state to test my hypothesis.
Bottom Line : you may need to pop a "Please wait - converting replacement rules" modal dialogue - maybe with some sort of progress indicator.
I would be wary of relying on spinning pointers. In Windows 10 the pointer is sometimes misleading. For reasons best known to itself it sometimes gets 'stuck' on a specific pointer e.g. the double v. bar or the spinning wheel etc, the only way out that I know of, is to logoff/logon - it's damned annoying when it happens
BR