I have the latest FW 3.63 running on my RPI. I have currently replaced a Solarcharger 150/60 with a 250/60. This has the same unit ID 239 as the shunt, which has been running in the system for a long time. All components have the latest FW and the Venus OS has already been rebooted.
OK, so only remedy I know would be to roll back to the earlier release that works. If you don’t have any specific issue with the older firmware, then there is not much point in updating.
Victron only recommend updating on major upgrades, new system or to correct a known issue affecting performance.
You can change the VRM Portal instances, which is the same number as used for the Modbus-TCP server Unit IDs in the Settings → VRM → VRM device instances menu: