Lame when driven, not ridden, ideas?

[millikins]

Hi, I have a 15hh Welsh/Hackney currently being broken to drive by a very well known carriage driver. The horse has been in the cart 3 times, has pulled it without issues but is markedly lame on near hind when finished. This resolves within 15mins and he appears sound. He's been broken to ride for 16 months, has never been lame schooling, hacking, jumping or lungeing. Should I be worried or is he just using new muscles and needs to build them up. Anyone had any experience like this? Thanks.

 

[Tinsel Trouble]

I would get a back person out to look at his sacro-illiac joint and muscles, and stretch out his shoulders and back legs before he's worked!!

 

[Goldenstar]

I agree with the post above but would also get the hocks flex tested.

 

[millikins]

Thanks, he's home for two weeks from tomorrow so I'll get someone to check him out.

 

[Toffee44]

Very good good breeding (I have a hackney x welsh mare also driven/ridden)

How old is he?