Sporadic problem with H265 encoder box and Pluto

[G4WIM]

GB3FT is just about ready for deployment but I have noticed a minor problem from time to time.
FT uses a chinese H265 encoder (fw version ENC_V1.62.190930 ON-DMI-16D) driving a Pluto running F5OEO V2908.

Both the Pluto and encoder box have static IP address and in theory the Pluto should control the encoder box.

The problem is that while Pluto is setting the encoder as per its strategy it doesn't see the multicast on port 8282 from the encoder - Pluto just reports null packets, then after a few minutes it starts to work with no problems for hours on end.

The problem is present even if I point the Pluto to the wrong address for the encoder control and pre-set the encoder from its webpage.

The RTSP output is always present from the encoder - just seems as though the multicast isn't being picked up by Pluto.

I've tried a range of multicast addresses on the encoder but always the same - null packets.

I have IGMP snooping turned off on the router, turning it on makes no difference.
I suspect the encoder is simply not going into broadcast mode for whatever reason - but can't be sure.

Maybe I've got a setting wrong some where - the F5OEO documents show multicast on 192.168.1.104 for the encoder - I suspect this is wrong.

Any ideas ?
I'm sure the problem will get worse once it's deployed !

73 Tim