Colorsource Spots and Pars stopped syncing on Net3 Concert (v.

We have recently discovered a problem with some (35) of our Colorsource Spot and Colorsource PAR fixtures not syncing on Net 3 Concert. I initially thought the problem was occurring with all the fixtures that were being fed from a 4 port gateway via Artistic Licence versaSplit DMX/RDM splitters, but on closer inspection it also includes 6 CSPars which are directly connected to a one port gateway. The fixtures can be seen on Net3 Concert but do not finish syncing (the update bar doesn't complete), and we can see the fixture name as "DMX start addresss... but none of the other paremeters are available and nothing can be edited. This is happening on both our lighting laptop and the desk (ION Xe) version (V4.0.2)

On one lighting pipe we have 8 fixtures running from a one port gateway: The 7 CS spots won't sync, but the Series 2 Lustr in the middle of the pipe does sync.

Grateful for ideas how to solve this. T.I.A.