Weird behaviour during shutdown.

Hello,

Since I have changed my GPU in my Mac Pro (RX580), the shut down sequence sometimes presents strangely distorted screens.

(e.g. see photo).

The GPU is not faulty, works fine. Tested with Cinebench, good score, intelligent fan control system working. The shutdown sequence is the only one process which presents such abnormalities. May it be because it is not original Apple GPU?

Please note it is not always like that. The one I uploaded is the worst one that happened.

Sometimes it does nothing (black screen with or without cursor), other times it displaces the rolling progress circle (you can see it in the left high corner, the small dots).