I got down on my belly with a flash light to see if I lost any sweet potatoes under the storage bench in the kitchen. I did, and they are perfectly good, wow.
But I also found this. I forgot I put these down there. They are form the only TPS plant I had last year that made seeds from seed. Rather than rotting or drying up the two or three ping pong ball sized tubers converted themselves into a bunch of pea sized tubers and roots. Never saw nothin like it. I wasn't working with TPS this season but guess I have to put these in the ground and see what happens. I got a spot where I been dumping weeds and such so I think I'll just poke em down in it and see what happens. It's in a little afternoon shade too, maybe that will compensate some for being planted so late.
I have seen this before. Usually it is due to tubers that stored poorly, and/or aged seed tubers. It is a survival strategy where the old tuber is trying to produce a new storage tuber before it is too aged. Unless this is a short dormancy diploid, the new tubers here probably will not grow this year without a dormant period. You may be better off separating them and storing them for 30+ days, then planting.