Years ago, We often encouted "out of sync" problems during our Xtreme Session. Initially, We guessed it may caused by the network latency and tried to imporve our network, but the problem can't be elimnated. This type of problem being lasted six months until I found the root cause.
The problem is in the database where there is an illegral trace records( I guess the Xtremepcb done the illegral records and Mentor may claims it is caused by the network flicks ^0^). You may export layout hkp and decrypt it, then seach string "lyr_2xx", you may find some traces be in the non-exist layers.
We normally have 3-4 concurerent desingers working on the same design and the "out of sync" problem is gone for ever now. If designers are new to EXpeditionpcb or Xtremepcb, I guess you may encount it often becasue they don't have experience to co-operate and don't know how to effectlly use the tool,it may make Xtremepcb overloaded and done the illegral records.
I tried to find the "lyr_xx" in the HKP, but it is not in the saved database.
Do you have an additional hint, when to look for it?
Ricgt at the time where the out of sync happens?
In the local copy of the client or the layout_temp database of the session?
I mean such as "lyr_254". You may try to search and list the string of "...ROUTE_LYR LYR_2" using ultra editor to see uncommon lyr_2xx.