Just to say - for a little perspective, my usually calm, safe, lovely horse turns into a complete and utter nutter who I'm tbh scared to ride with insufficient exercise and/or turnout. Sane on 24/7 turnout, and sane when turned out 8-12 hours + regular fast exercise, but quite crazy if either no fast exercise but still turnout or no turnout but still exercise. And she has NOT had any bad experiences, she's just highly strung!!
Also, horses with issues (got one of those too!) often bond strongly to their owner as they see them as 'safe'. If your horse is seeing you less than he used to, he will start to act up more as you're not reinforcing your relationship constantly and he's being left in the care of people he obviously doesn't trust if he's become head-shy.
Regarding the person who showed him - I too would say get in touch. Bet you could get some good advice there. If possible meet them too. Some people are naturally more assertive/unflappable and they make scaredy horses feel safe by their strong leadership.
Also, horses with issues (got one of those too!) often bond strongly to their owner as they see them as 'safe'. If your horse is seeing you less than he used to, he will start to act up more as you're not reinforcing your relationship constantly and he's being left in the care of people he obviously doesn't trust if he's become head-shy.
Regarding the person who showed him - I too would say get in touch. Bet you could get some good advice there. If possible meet them too. Some people are naturally more assertive/unflappable and they make scaredy horses feel safe by their strong leadership.