For us, the game crashed roughly five times in the Immaculate Village in the Luculla Forest. Three times while trying to trade with Masamune and twice with Attenberah after winning the conflict with her. Each crash seems to happen as soon as the first person has completed their trade.
This all began as soon as we happened upon the town and went to meet the merchants for the first time. Every subsequent crash was just us trying to complete the first transaction. (So no idling or anything like that.) We admittedly didn't try this in single player.
We were able to trade, battle in the game seemingly everywhere else without issue for a few hours after this.