How to lock folding?

Hi all,

I was wondering if the folding state of a file can be locked.

The editor very easily unfolds current folds, which to me is very annoying while working on a specific function in a file.
This seems to happen random and I've noticed also that it unfolds unrelated folds.
I use now PS-130.1293 but it happens in all previous versions.

Thank you in advance for any info on this,

Cornelis.