I have a breeding room consisting of two farmers. I place down 5 beds to breed 5 more villagers and once they're grown, I give them each a jobsite and they all take up a profession just fine and at this point I haven't traded them yet. I take one of the new villagers and minecart it to its holding cell (~70 blocks away, same ylevel) and it retains its profession. I go back to the breeding room and break its jobsite and I go back to him, he is now jobless. I try to place his jobsite in front of him but he won't take back his profession. The other villagers have still kept their own jobsites, they haven't stolen his. 

I have about 30ish villagers in holding cells each with their own jobsite but none of them are stealing his jobsite, because no green particles are showing when I place it. I have tried moving him to a different position, changing the jobsite, and even moving him back to the breeder room, but he will no longer take up a profession.

I have killed him and tried with another villager and the same thing happens, they refuse to take up a profession when I move them out of the breeding room. I managed to get one to work properly, by just minecarting him out of the breeding room and moving his jobsite to the holding cell, which was the same process as before and I guess that's just a fluke