My horse went through something like this. Turned out his new environment stressed him out and he was developing ulcers. Whenever he starts acting “hot” and ignorant I start him on a round of omeperazole and he calms right down within 2-3 days. I haven’t had him relapse since starting smart combo.
Our last move we moved countries and from a frigid climate to a warm one. In preparation I gave him a month of omeperazole before and after. He did the move like a champ and didn’t have a single grumpy day during or after.