Dark border on Lightroom Classic thumbnails

I have a problem with Lightroom Classic 15.3/Windows 11 (25H2).
(Ryzen 5900x - Nvidia RTX 4070 Ti - 64 Go Ram - Drivers at last version - Softwares localisation = FR)
After some work, I get black borders around the thumbnails and LRC becomes very slow.
Closing/reopening LRC is fixing the problem up to the next one, few minutes later.
It seems to happen when using denoising or AI masks and being an indication of graphic acceleration lost.
It is known? A solution?