I'd say the same. I also wonder abouit that harness - is it making a possibly incorrect situation worse?PUPPIES can do some weird stuff with their legs at times. The angle of pictures make it hard to tell what is going pictures from the side or head on rather than from over the top and behind. There are are couple that appear to be abnormal but can't say for sure.
How much exercise does he have/has he had because it's never a good idea to overdue with a Basset of under 6 months. Running around without being 'forced' and not on hard surfaces is ok, within reason. Is he allowed to jump on and off (more importantly) furniture (and onto slippery ground) or stairs? I remember a lovely couple who had one of mine who proudly described how he 'woshed' down their short flight of stairs onto uncarpeted flooring. Shudder. Have you been able to have his breeder take a look at what's going on - vets don't always have good knowledge of Bassets specifically unless they have many clients with them.