1999 Chevy Blazer brake/reverse light

I was just curious if anyone would know why my brake lights and reverse lights would come on at the same time. All bulbs were checked and are fine. Any help would be appreciated. Thank you

when does this happen ?

What year and model would help. Try checking to see if you got the right bulb and harness in the right hole of the lens.

It is a 1999 Chevy Blazer LS. All bulbs are in the right spot checked and are fine. I have a towing package on it as well. I am thinking something is probably shorting out from the wires for trailers. This only occurs when i step on the brakes. I could be wrong but any other insight would help. Thanx

My 2000 silverado has a plug within 18 inchs of the trailer brake control near the brake pedal unplug the connection and check. If this fixes the problem you know what to check. Just follow the wires from the controller they go to this plug.
A brake lite switch is near the brake pedal also. Then check the reverse switch.
The manufacturers put this plug in to prevent people cutting into wires with improper connections.
If you didn't use the plug locate it and buy a proper connector. Most trailer companies,U-haul and Northern supply sell the plugs and tell you what wires to hook to it.