Presets not staying applied

Hi,

I have a possible bug in my LR (Classic CC) which is driving me crazy. I can apply my presets on import with no problem, but if I apply by clicking in the drop down list in the develop module, then about 50% of the time the preset does not stay applied. Instead, if as I move my mouse away the cursor hovers over another preset for even a fraction of a second, that preset shows instead. Sometimes when I move my mouse away from the list the photo just reverts back to whatever it was before I tried the preset at all, sometimes the incorrect preset stays on. It's almost like the main photo preview in the centre is behaving like the thumbnail at the top of the preset list, if that makes sense? It's continued to happen through a few updates, it's been happening ever since the change to Classic CC.

Any help appreciated!