Horse lame in LF hoof need help finding solutions?

I have a five year old appendix gelding who had been lame in april on his LFon and off for 3 weeks and after a nerve block to the foot we determined the lameness was in the hoof. Xrays and ultrasound were clean so the vet injected the coffin joint and we gave him a 3 weeks rest and he seemed to be back to normal. He returned to normal work for over a month and then he was "ouchy" when i went to ride him on a monday, by tuesday he was at a 3 on the lameness scale. He had no heat, pulse or reaction to hoof testers. A different vet came out on Weds. He did a nerve block and determined lameness was in hoof again. He pulled the shoe and decided to treat for a bruise or abcess first before we jump to other things. We wrapped the foot and have been soaking for a week with bute for first 3 days and he seemed to be getting better. I am going to have the farrier put the shoe back on but since this has happened twice and two vets have done two different things could it be something else.