Getting to grips with ArtNet

[Techie_v2]

Hi all,

I've got some fixtures (Showtec Octostrip) that are Artnet capable but I'm having an issue with them. 

The first unit I can connect and control with no issues but when I connect a second unit (either through the built in artnet out port on the first unit or with both units connected to a switch) the second unit freezes every 20 seconds or so, for about 6 seconds then carries on what it's meant to be doing.

Both units show up on the devices screen on the desk and I have tried various different configuration like static IP's, using a dchp server, using different ip ranges  reseting them to factory settings etc. If I connect them with dmx they work fine but for universe reasons I need them to work with artnet as I have 3 units each taking 192 dmx channels, plus the rest of the rig.

Anyone any ideas?

Thanks