I now suddenly have exactly the same error and also a faulty, undeletable asset in MH. Since just now, I can no longer log in to QuixelBridge, and as soon as I open Quixel, the entire engine crashes.
Reinstalling Quixel did not help; the error only occurs for me in version 5.3 - 5.4 works perfectly fine.
I think it’s an error on the part of Quixel or MH.