Thumbnails view reseting

Hello everyone,
I would like to have a thumbnail view for all my folders, I set it in the folder options, but it keeps resetting automatically randomly (as far as i think) or when I restart opus. I used the lock in the state bar, which I hide then because I don't need it, still resetting.
How to avoid automatic view changes of folder? In other terms, how to force thumbnails view for every folder all the time..?
Thank you
fabien

[Folder Formats: Quick Guide)

thank you... :blush: