Thank you! This summer, at training- he was on Ulcerguard. Currently, he has Tract Guard in his Smartpack as well, so although I cannot be 100% sure, I am not sure if ulcers would be the issue. Of course, there can always be more than one thing going on with horses too.
No vet has really mentioned neuro issues. He was tested in terms of backing up and otherwise just did not seem to exhibit any other neuro symptoms. I would look into that if I fail to find a soundness issue that can explain his symptoms though.