Lighting, Light Fixtures, Ceiling and Exhaust Fans - Another 3 way switch issue but different

I have a bad "duplex" type "duel" switch. Two switches controlling two different lights all in one unit. One side of the unit controls two shared lights in the garage. And the other side controls the inside hallway leading into the house from the garage. In the garage I have one on-off switch for those lights and in the house I have another single next to the kitchen to turn off the hallway lights. Both switches are used when entering and existing the house.

The house was built in 1977 and everything has worked fine until last week. The inside switch controlling the garage lights froze in place and will not move. I went to our local electrical supplier and proceeded to change out the faulty switch. I removed one wire from the old switch and installed it to the new switch. All wires removed one at a time.

Turning on the breaker the following happened. Both opposite single switches are functional. The one in the hallway and the one in the garage. The new duel switch duplex does not operate. I did remove the tab between the two black screws that connected the two switches. The new switch looks like the old switch. Two black screws on one side and four copper screws on the other. Where did I go wrong? Could the new switch be faulty?

Did you buy a three way dual switch? What did you connect to the brass screws?

Yes, I bought what they said was a three way switch.
One black wire to each black screw
One set of red wire to copper and one white wire to copper

So what I ended up with is, two each black wires to the only black screws and three red and one white to each copper screw. Like I mentioned before, I only took one wire off at a time.

Switch positions with the two black wires. You may have them backwards.

I'll switch them around and see.. How it came off is how it went back. Thanks.

Chandler. Switched the blacks one on the black screws and one switch did not work at all. The other worked in the house but did not work from across the garage.

If you connected them back the way they came off the old one and the old one worked, I am at a loss to see why they won't work. Was the tab broken on the old one, too?
Are the red and whites from the same cable connected to the same set of brass screws? Just stabbing, now.

Yes, the brass bus bar tab was removed on the old switch as well. Three red wires and one white wire. Left side of the new switch has two black screws with two black wires connected from the house side. Right side of new switch has three red and one white wire assuming coming from the lights?

I'm not intending to sound redundant, but the reds and white, did you happen to cross any of them up? Are they in cables or are they separate wires in conduit?

Finished up for the evening. Here is the latest... I have one set working to design. To make the inside of house to garage lights work from in the house I removed the black wire off of the black screw and placed the black wire where the red wire was. Placed the red wire on the black screw and it works from in the house and in the garage.

Now for the garage to the hallway switch nothing. Still operates only from the far end of the hallway switch. I believe the new duplex switch has a bad internal part? Will buy a new switch tomorrow and start all over. Will keep you posted...