If he's constantly tripping (like every time he's ridden, multiple times he's ridden) then no, I wouldn't write it off to being a walker. I just wanted to pop in and say that walkers can trip more often (from my experience) when not balanced by their rider.
I don't believe the walkers there are left with long toes, as I remember one of the BO's asking the farrier to not leave long toes, if he does, we have him correct it.
Please don't take just my advice into consideration, I probably should have stayed silent, but I did want to offer what I know about walkers into the conversation. I am by no means an expert, but after riding alongside them for many years, I have picked up knowledge here & there.
Best of luck, OP, sorry for any misunderstanding. Hope this problem gets sorted out and you have many good rides with your TWH.