There are a number of factors that could affect this:

- network switch
- network data
- cable length

Network switch
Ensure that the switches can support broadcast data.
Unmanaged switches are the best to use - cheap netgear / linksys / tplink are usually ok. managed switches can filter broadcast packages and may not work well

Network Data -
best to use a separate network for Remote desktop and file transfer - as this WILL slow artnet down if on the same network.
Do you have other artnet devices on the same network?

Cable Length
This might be a factor - but test the other 2 options first.
The only way to test is to use a shorter cable with the same network setup and and see if it makes a difference - this may mean temporarily moving the desk nearer the servers if possible...
You could also look at getting a fibre link between your locations. there are a number of switched that have a fibre port and thus avoiding any cable length issues.
however - I've run 100m cat5e networks with no issues... so do check the other possibilities first. (cat 6 may help?)

Also try UNICAST artnet from the MA2 rather than broadcast, as this will reduce the amount of data... although, this may not work for your main/backup scenario...

Best to remove all other devices from artnet networks and use a separate network for remote desktop and file transfer.

Simon