Hello again!
Per your updates, there’s definitely something going on between Quixel Bridge and UE, and since you have already cleared most options related to your local setup, the remaning path is to inquire about the bridge, directly.
Since the feature has been incorporated into the FAB layout, support for it can be requested in the following site below. Please make sure you include a detailed description of the issue:
https://support.fab.com/s/?ProductOrigin=Quixeltier1&token=676nFmFdYVXX6ZpV8H95Sr8SZFFEZSyvJkpo