White areas randomly appears, it's not a display issue, but it's not pixel neither...

I worked on a fil with a lot of layers (smart objects) . It's an animation .

Everything was going well during several days, I made several version of the file. The files were ok, and the export in MP4 were ok too.

Suddenly, big white area (square shaped) appear on every smart objects, avery layers:

It's not a previsualisation probleme, as this areas stay at the export. I can even modify them with the tools. But that's where everything become weird:

(There is a video to show the 2 exemple i'm talking below)

- if i try to erase them, it create others

- if i try to hide them withe a layer mask, the layer mask do not "obey" to what i'm asking it to do : my selection is note taking in account, and a new selection is created, you can see it on the layer mask on the video: i creat a square selection, and the mask create a revers L.

(There is screenshot of the 2 exemple i'm talking below)

- I wanted to save my file in JPG, to see if the white would stay : I can't save my file in anything else than PSD, TIFF, PSB and few others. JPG PNG etc isn't even proposed on the liste

- So i try to flatten the layers before saving, and the white areas changed shape (if i undo the shape go back to what it was, but each time I flatten it changes)

I've tried:

Turning on and off Photoshop & my mac, Unstall/Reinstall Photoshop, disable graphique card.

The shape of the areas are always the same on eache layers, they do not desappear/reappear, they are always there, in the same shape.

One last information:

This problem appeared because of one file. Then, every file I tried to open had the same problem. After a night of break, I tried to work first on the other files and everything was ok. But as soon as I reopened the file that caused the problem, the problem reappeared. On each files. So it's like this file activate the probleme, but then the probleme stay for all the day, on all the file (even a really small simple file)

Technical informations:

Last version of photoshop / Mac, Big Sur / AMD Radeon Pro 5500M 8 Go

Any idea... ?

Thanks !