Fill no good, 1-1 fine.

This is a problem I've been having for a while.  I have a Mac and 32GB ram, so plenty.  I do LRC adjustments and later come back to view the photo in Fill mode.  Many of the changes are not seen, it's not crisp, the texture and shrpening not showing for example.  I wait and wait and nothing.  If I go to 1-1 View, takes a few seconds and then changes are shown.  Then, if I switch back to Fill, all OK.  But if I go to another photo, and then come back to the previous one, I start all over again with Fill no good.  What's the problem?  Thanks.