I don't know if it's the size. I got Peanut from someone on this board. He has 1 teste that hasn't desended, 90% of his adult teeth and still 90% of his puppy teeth so his mouth is a mess. Now I find out he has liver issues almost certain a liver shunt. SO I don't know if it's because he is a tiny...he jsut reached 3lbs at 1 year or if it was because of bad breeding? !
Who knows, I know this last issue has me bonding with him more and really babying him. So yes do your homework before you purchase.