Multiple 3-way switches and a GE Z-wave on/off

Ok, hopefully with the below image someone out there can help.

I have a 3-gang box with four sets of wires coming into it. 3 sets of 14/3 and one 14/2. Power is supplied on the 14/3 bundle in the middle top of the box. The far right wire bundle has a 14/2 going to a porch light.

The top left 14/3 goes to another 3-way switch at the top of the stairs, and then from what I can tell to the light fixture. The back of the box (middle) 14/3 goes to a hallway light and then down to another 3-way switch. The far side of this 3-way switch has the black on the load and the white/red connected to a traveler.

Everything worked fine before I tried hooking up the GE Z-wave into the box to control the front porch light. I tied a lead from the neutral bundle into the z-wave switch and everything worked for a short period of time. The stairway light seemed about 50% dimmer than normal, then stopped working.

I am able to get the Z-wave and the hallway light working, but cannot get the 3rd light (stairway) working.

I was running all of the blacks into one bundle and then one lead out to each switch (one z-wave and two ‘dumb’ 3-ways). All of the neutrals were tied together.

I have a red coming in with the power bundle but I can’t for the life of me figure out where it goes.

Any help would be greatly appreciated.

The red will typically be the line to the other switch in a 3-way, the “traveler”. Red isn’t used for “power in” as you have described it. Power is always on black (hot) and white (neutral). I’ve never seen red used except as a traveler, but you could have something I’ve never seen very easily. You have to pull the other 3-way switch out of its box too, because it’s very hard to tell where the voltage is coming from (i.e., could be coming from the other switch).