Unfortunately, this is not related to cloud issue. It's just a normal folder redirecting via your folder portal system.
I made a gif to illustrate my issue. "Games" fence is working super smoothly, but the two others (it's the same file actually, named "utilitaire") have this blinking, no matter what i try.

You mean that you don't have that at all and that your folder portal created display the files as smoothly as the normal fences? (and what if you put many files in the said folder, or maybe it depends form which hard drive it comes from, i don't know)
I really thought that it came from the software (due to the fact that Fences has to fetch that file content everytime it rolls back up, thus the reset). If it's me, I have no idea what could have I done wrong. I don't have anything really fancy installed on my PC that could conflict with that and i usually don't have any issue like that. My W10 is updated as well.
Any idea of what i could try to do?
Thank you.