Neu motor hex size?
 

I need to resolder the wires on my motor inside the can but I'm not sure what hex the grubs are that hold the ends on.

They are TINY! Never seen them so small.

I'm guessing Imperial too? Any know what driver I need?

Not sure you can solder inside the can... The external wires on a nue are the actual end of the windings...

Don't mess with them as they are lacquered which is a PITA to remove and resolder - Thats why you can't shorten the wires on an original Nue

The motor wires aren't getting good contact though, they are loose so a slightly knock can make the motor jumpy.

What would you advise?

Send it back to Neu I'm afraid. Sounds like the windings might be shot. Thats why they moved to rubber grommets around the output wires and Castle changed the design completely...

There is no point opening up the can with any hope of repairing wires... At best you will invalidate any warranty.