After hunting for the add-on that was causing desyncs even on default era games, I finally tracked it down to this add-on.
Wesnoth 1.18.2
If one player has Everfell, and the other does not, desync on recruit is caused. Most likely the problem is with custom resistances for energy, that cause the unit checksum to become different.
EDIT: it does not seem to affect normal multiplayer scenarios, only random and custom maps.
https://github.com/wesnoth/wesnoth/issues/10010
Wesnoth 1.18.2
If one player has Everfell, and the other does not, desync on recruit is caused. Most likely the problem is with custom resistances for energy, that cause the unit checksum to become different.
EDIT: it does not seem to affect normal multiplayer scenarios, only random and custom maps.
https://github.com/wesnoth/wesnoth/issues/10010
Statistics: Posted by Jarom — Yesterday, 8:30 pm