Build Number 1.10.2
The end turn timer is abnormally slow since the new dlc for the AI factions. It seems to work for a turn after accepting a resync.
Retracing our steps:
1) Start game save may immediately need a resync when starting the game.
2) Skip all notifications and press end turn.
3) Next player does the same.
4) Repeat steps above for one to two turns to receive another resync attempt window.
We have played on Lan and online to see if anything was different and its the same for us.
We are also playing Belegar and Durthu factions if that information helps at all and my partner has not recruited Ariel at all but have seen that in the patches notes she may have caused a desync.
Hope you find the fix for the desyncs!