Is there anything that can be done about this U5215 universal motor?
A motor like that has brushes; carbon piles that make contact with the rotor. they are likely worn out / dirty. You can see the holders for them, they are the squarish brass tubes on opposing sides. In addition it looks as though your commutator, that part that the brushes make contact with, may be dirty and/or worn out as well. Most cheap little appliance motors like this do not make the brushes replaceable and 'servicing" the commutator is less than practical. 

It has "shuffled off its mortal coil"...