Loosing slide layout setting

I wondered, is anyone else having issues losing their slide layout selection? I am applying my layout in the normal manner, but when returning to the .story the next time/next day (or whenever), randomly one, two or three slides (always different ones) in the file will have lost their master slide setting, returning it to a blank setting, but still showing the correct master in the thumbnail at the left of the screen. In 10 yrs+ using Storyline, I've never seen this, then for the last few weeks, every day. I can check all slides are good, save, exit Storyline or just close the .story, open it again and they are randomly gone. I will report this to support, but wondered if anyone else had experienced this? Thanks!