Definitely not NixOS-specific, so it would probably be better to ask in some other thread.
But anyway, are you sure that this error actually appears right after the disconnect? Does it appear every time? Many people are getting this error, so it would be good to confirm that it is actually related. My logs are definitely full of this error and I don’t think it has any negative effect in my setup. You might also consider following e.g. [RESOLVED] AMD F39 USB-C hiccups with external display directly connected via USB-C - #16 by Matt_Hartley.