More specifically I originally had one set to control NATO faction, and then one to control RHS army faction and one to control RHS Marine faciton. Even if I only have 1 just Nato as I was going with no mods so I couldn't put in the RHS factions it wouldn't save for some reason. Even once I switched to a local database thinking it might be easier with less networking issues.
When you say only 1 per side is that per faction or side? I've currently got multiple from Opfor side, but different factions for each and it seems to work fine. Albeit long load times and save times but a small price to pay for a battlefield that feels genuinely ALiVE.