Undescended testicles are a health concern for dogs.. and I have heard that also about "not" being able to remove them even during surgery, however now days with so many specialist, that is who should be doing that kind of surgery… IMO....
Also, wanted to chime in about a 4 month old with an undescended testicle.. I would wait until at least over 6 months.. especially with a Basenji. In one of my litters, we had a pup that I could find both at 2 wks, however at 10 weeks I could not, nor could my Vet... He was placed local, so I was able to see him a lot and it was not till he was 7 months did the other testicle drop..
Basenjis also carry their testicles different then other dogs, which is another reason people have problems (even Vets) finding them.. instead of like most dogs that carry them side by side, Basenjis carry them one in front of the other... which I suppect is the reason it is so easy for them to "suck" one up... and yes they do that.. especially puppies... Cold hands from a judge and you can bet they are gone!... Many judges will have the handler take them off the table and move them around the ring and then re-check....