This is 100% a problem of one or more players using two or more PC's to play HexWar.
The HexWar server only stores the most recently uploaded game turn.
When swapping PC's it is essential to click Send/Receive at the start and end of every session on HexWar.
Otherwise when changing PC's a game may revert to the state last played on the current PC rather than the last state played on any PC.
The launcher tries to manage this automatically but the nature of different users broadband connections can prevent different PC's used by a single user staying in sync automatically.
Clicking Send/Receive at the start and end of every session on HexWar solves everything.