I assume you are saying you have to hit the switch several times before it retracts the slides. But once starts retracting, then it completes with no stoppage. That implies it is the switch. It is inexpensive to replace. But if you wanted to verify it is the switch before you spend and money, here is what you can do.
This is a Double Pole Double Throw switch. You can swap the Retract wires with the Extend wires and the problem should now be with the Extend function (the IN side of the switch). Retract (now the OUT side of the switch) should work just fine. This demonstrates the contacts for the IN side of the switch are failing.
If the slide stops during Retract and you have to release the switch and then press the switch again, I would look at replacing the 12V self-resetting circuit breaker leading to the pump assembly.