my milwaukee m18 drill driver won't go into reverse, the switch is stuck.

The forward/reverse selector switch is likely jammed with debris or has a broken internal component.

Fix:

1. Remove the battery pack.
2. Clean the area around the selector switch thoroughly. Use compressed air to blow out dust and chips.
3. Apply a very small amount of electrical contact cleaner to the switch seam and work the switch back and forth.
4. Wipe away any excess cleaner.

If that didn't work, the mechanism is damaged internally. Do not force the switch.

Heads up: The selector switch must be fully in the forward, reverse, or center (lock) position for the tool to operate. A partially engaged switch can cause intermittent operation or damage.