Tier2 drop during offseason

Fisefar

After a bumpy season we where able to reach tier2 multiplier and expert map, still at plat3 rank tho. every war in off-season we have been playing the expert map, but these last two wars we suddenly got bumped down to tier3 war/challenger map.
How is this possible?

MrSakuragi

You matched with alliances the tier below you and played on their map. This happens particularly when you’re on the edge of one tier and have a war rating slightly higher than those below you.