
unless there was another trumping reason to breed the dog then probably hold on to the endorsements. i mean that if the mouth was overshadowed by perfect conformation in every other respect then maybe it would be worth it- i don't know much about showing bloodhounds sam, are they a 'head' breed? given their appearance i'd assume so, as such it depends how much of an effect the mouth has.
the grumbling could be a number of things- bad temprement or as is suggested above simple "growing pains", his owners, breeder and breed experts like you would be best fit to judge having observed the behaviour and as such consider if its likely to be passed on.
we put endorsements on for a reason, we should stick to them. if the breeders got issues with pups coming from this dog then i say no- i think breeders need to think along the lines of "if i was getting a new dog would i want one out of this one?". i think from what you've said the answer would be no.
additionally you've a numerically small breed- but not critical, and you've mentioned frequently the need for a specific type of owner. as such i'd say only mate the really good ones (as we all should really). if the breed was really struggling and needed the mating to survive then yes but i think (please correct me if i'm wrong) your breeds numbers are fit enough to survive but small enough to keep them with the right sort of owners, they seem to have a healthy balance. as such whats the need to produce other than great quality pups?