Lightroom Classic 12.4 edits not showing

My Lightroom Classic v12 has started acting up. My History panel shows all of the edits I made but the image periodically stops showing these edits!! Stepping back through the edits has no effect on the image….

Sometimes switching to Develop mode or back to Library mode reinstates the edits but not always and they don’t always stick around even though they are still showing in the History panel. I’ve tried taking Snapshots when it is working and making Virtual copies. It doesn’t help:(.  Rebooting helps sometimes and then only temporarily.

I can’t find any help on-line…. Can anyone help?