Slides won't retract...

What usually happens with those older motors (ones on mechanical leveling legs, too) is that over the years the brushes wear, get stuck, or get a coating of dirt keeping them off the commutator. It can be a simple fix if you are somewhat mechanical. If the motor can be removed, disassemble it, clean the commutator with very fine sandpaper (not emery, it leaves conductive grit), make sure the brushes are clean, ok and free in their holders and reassemble. I use lacquer thinner to clean off the brushes and their holders. Reassembling can be tricky as you have to devise some way to hold the brushes back against their springs while you get them over the commutator. Getting the armature back into the shell can also be challenging since the strong magnets will yank it out of your fingers on the way in (and pull the commutator back out of the brushes you just struggled so much with!) The take-away from this is that regardless of how old the system is, the little motors don't really get that much run time so are rarely ever 'worn out'. The problem is usually poor contact between the brushes and commutator due to years of dirt/grease buildup. Some fresh grease for the bearings is also called for. When you work on it, just be careful not to damage any of the motor windings (the magnet issue is a real problem there). Quite often you cannot buy just a motor and since it's likely that yours is not really 'bad', just dirty, it's well worth the effort to try to clean it up. Chances are, this will add another 10-20 years life to the motor. There used to be lots of motor shops around but they are mostly gone now and except for rewinding big industrial motors, the few left are only interested in selling you a new device (which will include the entire pump unit).