Interesting issue, I tried to reproduce it and initially failed. After comparing what you had more closely to what I had done I found the missing puzzle piece that broke the RPC, and that was Set Default Controller.
It seems having an AI controller somehow messes this up, but I do not understand what is going on. It can be fixed by setting the owner of the controller to the same client PC, but again I could not say why sorry, as I totally can’t make sense of this and my attempts to research it are leading nowhere.
If anyone out there can explain, please please do… I can see some sleepless nights ahead (JK, but would really love to know what is happening here).