My 'UP Browser Extension' controller ran out of LYX. For my transaction, I thus switched to the UN1.IO Antica Relayer. However, it was impossible to conduct transactions from that relayer "Could not fulfill the request (internal error)."
The UP got subsequently stuck on that relayer and did not allow me to change to any other relayer or back to my controller (see screenhot). I am not shown any option to do so on the transaction page, nor in the advanced view. In order to change back to my controller, I had to enter the UP settings and delete "UN1.IO Antica" which was listed as a custom relayer. This led to the relayer being deleted permanently and I can not reselect it now.
This seems like a bug and should be remedied.