Reverse light problems

I recently put new headlights taillights and everything on the truck and the reverse lights worked for a couple weeks and now they come on when they feel like it. Any ideas on why the brake light, running light will come on but no reverse? My guess is the switch in the trans. Also I haven’t adjusted the headlights yet. Wondering which screw would be up and down and side to side.

 

Poor wiring or connection since they're aftermarket.

Try putting the originals back on and see I'd they work...

 

I feel like it may be the reverse switch. If it was a poor wiring/connection then none of the lights would work. Or one side wouldn’t work like it should. They both have running and brake lights just no reverse.

 

The reverse transmission switch is easy enough to replace, been there, done this.

 

Yea I figured it’s simple enough just seeing what others opinions on the problem may be.

 

You can probably use a jumper wire on the switch connecting to test it

 

Had a similar issue and it was the OEM reverse light switch. Mine had basically fallen apart. I'd start there.