MinimWatch only shows 1 instance

[MarmiteSandwich]

Sometimes I have 2 instances running in the same LAN. According to the installation instructions, "MinimWatch will display a tray icon for each MinimServer instance running on another computer or NAS on your local network", and I do remember a time when this was the case. However, for some months now, I only get 1 of them showing up in the tray, whether it is MW version 0.8.5.2 or 2.0.8. It seems to be random which one shows up. Both instances are identical apart from the displayName. Instances are both 2.0.16 update 178/Raspbian on Raspberry Pi. Minimwatch is W10 Pro, v1909.

Actually, UPnP control points (W10/UPPlay and Android/BubbleUPnP) seem to suffer the same way - only one instance shows up, and it is random which one.

Do they need to have different ports in the properties, or something?
Marmite.
PS the license details also seem to think I have only one instance, although I have activated the license separately on each one.