The same thing happened to my Neu 1515/2Y (magnet separated from the motor shaft).
Sending the motor from Europe back to Neu was no option for me as i didn't wanted to wait more then 2 Weeks (or longer). I reglued it myself and the next day i could drive my car with this motor again. I was suggested to use Loctite 638 or 648, but used a cheaper alternative brand. Did work for me.
But i still have a Neu 1512 with a broken shaft (next to the reglued Neu 1515 rotor).
I bought a new 5mm steel shaft but was NOT able to separate the magnet from its broken shaft. I think i should try to contact Neu if they know an "easy" way to loosen the shaft.