I recently had the Ultra FX card fitted to my desk, I rarely had issues using most theatre in-house Cat5 tie lines but now the desk has become very unstable when using anything other than a direct connection between the desk and stagebox
I don’t think installing the RUFX card changed any of this. I honestly think you just got lucky for a long time regarding un-supported non-direct connections between your stage boxes and the console and your luck finally ran out.
There is no question that the A&H proprietary protocols (GigaAce, DX, DSnake, etc) work best when there is a “direct connection”. In fact, direct connections are the only “officially supported” technique. That’s not to say that adding in network switches can’t work because they can, but it definitely adds a layer of complexity that can easily break the system if not handled correctly. For example, those non-direct connections are not going to work without a dedicated VLAN set up in the network switch for each and every connection between two A&H devices because you have to keep the A&H traffic isolated from the regular network traffic. I’d be shocked if the venues you frequent have dedicated VLANs setup for this purpose which would explain why it doesn’t work.
This A&H article is a good place to start if you are thinking about using “non-direct” connections. https://support.allen-heath.com/hc/en-gb/articles/45526905505425-gigaACE-and-DX-networking-VLANs-and-Fibre-Optics
Absolutely concur with Brian on this, I have used an Avantis extensively since its UFX card was fitted with no issues, and Point to Point is the best way to connect the console to the I/O rack. In fact this is the case for all Allen and Heath products. The only variation on this I use and would recommend is the use of media converters to take advantage of the benefits from fibre optic cables. I admit to having no experience with V-LAN systems but I understand that it should work but I would still go for a direct connection.
Regards