I am fairly certain the block piece under the shrink wrap is a thermo cut-out and it may be bad. It is wired in series with the motor feed line.
This was to save motors from burning out (in theory) when they were prevented from moving due to iced doors in the winter.
This is from memory and having fixed a few 28 years ago so I may be wrong but I don't think so.
I am sure I have a few used spares in storage.