Switch Contact 1611329024

Take handle apart
Take gear box off.
Pull out armature
Pull windings out
Replace Adapter module

On Handle side Pull Brush holder
Replace Switch contact.

Reassemble

DISCONNECT FROM ELECTRICAL POWER
Remove 3 screws from handle (square driver).
Remove the cover from the handle.
Take a picture to show how the wires are routed from the handle to the body of the drill. There should be enough slack in the wires that you don't need to disconnect any, but take a picture before disconnecting so that you can reconnect them properly.
Using tiny screwdriver or other small tool such as dental pick lift small springs holding brushes in place and move it out of the slot to the side so that brushes will slide back away from commutator.
Usually takes 5 or 6 tries before you get it moved to the side out of the way so it doesn't spring back against the brush.
Use small tool to push brushes all the way back in the slot
Lift brush holder off drill. If it does not come off easily the brushes are probably not all the way back in the slots.
This will expose the contact strips which you can't see with the brush holder in place.
Inspect contact strips.
Mine were pitted where the brush holder made contact for forward rotation.
I scraped the strips to expose fresh copper but could not remove the pits.
I coated the strip with silicone (dielectric) grease but put too much on the first time and had to disassemble everything to wipe off the excess grease after which the drill operated fine, but I ordered new contact strips just in case, because I don't know how long this fix will last.
To remove the contact strips, gently pry them up with a tiny screwdriver. Be careful not to bend them if you plan to clean and re-use them.
No need to worry about bending if you are going to replace them. I would coat the new contacts with dielectric grease (very thin film) to prevent corrosion, then gently press the three prongs into the slots.
As long as you have the brush holder out of the drill, inspect the electrical contact on the bottom of the holder. It is a small round "dot". If it is corroded or burned, now is the easiest time to replace the brush holder.
Also inspect the brushes. If they are short, consider replacing them also.
There is no easier time to replace these parts than when you have them in your hand.

To reassemble, install the new brushes in the holder but do not yet put the springs on top of the brushes. Install the contact strips, then gently push the brush holder onto the shaft until it is seated with the brushes on the commutator and the brush holder touching the contact strips. With a small tool return the springs to the slot to hold the brushes against the commutator.
Check the photo you took of the wire routing to get it the same way. Unless the wires are in the right place the handle will not go back together properly or you might pinch a wire and damage insulation.
Make sure the trigger goes all the way forward in its slot.
Place the cover on the handle, making sure the ball on the cord is properly seated and re-install the three screws.
Plug in the cord and make sure the drill operates both directions.
Cheap fix for an expensive, powerful drill.

read on your site that the Bosch adapter module & switch contact parts were the ones that went bad--instead of the $38 trigger. Turns out that there are 2 switch contacts AND 2 adapter modules needed (i only bought one of pair of each - my bad for not studying the exploded view more closely). Took the drill apart & visually inspected the old switch contacts. Could not find any fault with them. So I tossed the drill & ate the cost of buying the module & switch contact. Bought a DeWalt hammer drill & completed my project.