Why are the preview images in the filmstrip different colours and setting sto the main photo.

I use the filmstrip when I am copying and pasting the same changes to a lot of photos and use the filmstrip to check what I have done.  Sadly a few updates ago, some of the filmstrip images now show completely different colours/settings to the edited photo.  Often the filmstrip changes colours'settings when I click on the main photo, and sometimes it doesn't. This does not happen for all photos just a lot of them. It's really annoying.   Is it something I am doing or a bug?  I keep LR Classic updated to the latest version.   This never used to be a problem but started a few updates ago,.   

I am attempting to build a timelapse sequence from a night shoot.  The images were all take at the same settings and although the aurora changes it's not enough to throw out the settings.  

TYIA