Hi there, thanks for the reply, so we had just finished the main campaign and starting the Black tusk missions, so we went to the Campus settlement as this was flashing in the map and it had been overrun by the Black tusk ,but there was no difference and i couldn't buy from the vendor, i could sell, but not buy.
We left the settlement and headed away and came across some enemy in the streets, i thought we had killed them all, my indicator was clear but my friend was still shooting enemies and his were glitching and taking alot of bullets. The enemies he was shooting were dead on my screen.
I went back to ps4 version and back to the settlement where i could buy from the vendor again.
We will try again tonight/over the weekend with me on PS5 and him on PS4 as it may have been a one off situation but thought id see if there were incompatibility issues etc
Thanks for your time and help