This last year there I got to meet him in passing when he was going to practice and then be right behind him on court. It is something to behold. I have a short clip I had posted on Instagram of it.
See if this works.
https://scontent-lax3-2.cdninstagra...40_1757203984609459_6035665361511120896_n.mp4
I have a good hour of footage somewhere.
That said, he can be a very streaky player with the FH. Literally hit or miss, and I think as others mention it is because there is a lot going on to make it happen. It takes him a lot to time it, so when it is off it takes a bit to get back on. But when it is on...it is sooo on.
Also, I saw something above about it sitting up with the spin, but from what I saw he rarely hit with a lot of margin on the net and it wasn't coming up often.