heyyyy   id say wats wrg with him is that he misses his friends and the treks it will take him  time to ajust 2 the new place .   or else hes showing you a sign he mite  b ill or grumpy over sumtan    but id say hes just missing his ol livery yard .      mayb just get him used to the place  mayb even walk him around the stabls and let him get to know other horses !   and if you let him out with a herd of other horses watch him with them for about 10 mins and see bcuz he mite b left out or bullied and mayb hes upset and if this is the problem put him in a field with other horses  !   hope i helped! :)