Un Syncing accross DPs

Hi all,
I am wondering if there are any tips on keep the DP's synced to each other. I have fixtures on the same truss on seperate DPs and sometimes they seem to loose sync, especially when Fanning parameters...
For example:
When I grab Fixutres 131-136 (With 131 thru 133 being on DP 1 and 134-136 being on DP 2) and have a pan action with a fan fixtures 134-136 don't fan correclty with 131-133. It is a noticable delay with fixtures on DP 2...
I also sometimes see fixtures 'catching up' with each other when a cue is played back...

I am using a Gigabit switch (which is running in 100 Base t mode) and the Dps are at FOH connected with 25' EtherCon cables.
Thanks!
Robb
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