As things get older we need a boost at times.
The pot on the slide control needs a small adjustment to increase the current to the motor so it can get slide up your ramp.
Its also a good time to check ramp to make sure there is no screws or metal plated loose on ramp than increase the pot just in small increments until slide moves up ramp and to flat floor, may want to look at rollers also nothing loose there either.
This link will lead you to all slide information.