The problem is your existing wiring makes no sense.
First, I believe your recall of how it was wired, and I am relying on your claim that it did work properly before. The way you cut the wire off the old 3-way provides clear evidence. The evidence just doesn't make any sense.
Classical 3-ways are wired like this.
Your colors vary, of course. The travelers connect to nothing else. Now physically, the travelers are on the brass screws. I've never seen a 3-way with a bronze screw, but it's clearly the odd nut. So the travelers in your picture 1 are plainly red and blue, ok.
Except look how your red splits: there is no earthly reason for a traveler to do that. Could we be wrong about traveler colors? No. Your first picture after "update" shows the other 3-way, and it agrees: red and blue are travelers.. The only other thing I can think are the 3-ways are some sort of smart switch, but nothing on the back legends suggests that.
This much is fairly clear: the conduit stops somewhere else in between the two switches. Throws up hands I say nuke it from space, and start over. Here is what makes that possible:
This is EMT conduit
Which means we can easily install any wires we please. And also, ground is taken care of by the conduit itself, so it's off our plate. Also, I don't know what position the lamp is in, in all this, but it doesn't really matter where these things are ; we will connect whatever is required for this setup. There will be 4 wires:
- Neutral (NEU) - this is supply neutral. Mandatory color: white.
- Always-hot (HOT) - this is the supply hot. Color: pick one.
- Switched-Hot (SWHO) - this wire is hot when the light is on. Color: pick one.
- Signal (SIG) - this wire is hot or not depending on remote switch position. Color: pick one.
Now, you need to open up your lamp box and any other boxes in the vicinity, and figure out how the conduits connect to each other, and which wires go where. I like to pull on a wire a few inches and see if it moves in the other box. Don't pull on that white lol.
The next goal is to use your knowledge of the conduit route and the inventory of existing wires in that conduit to connect everything that needs to be connected.
- Supply Power: HOT NEU (always hot and neutral).
- Caseta switch: HOT NEU SWHO SIG to the switch's black, white, red and blue respectively.
- Remote switch: HOT SIG. That's it. If 3-way, leave one brass (traveler) unused.
- Lamp: SWHO NEU
- Power onward to other uses: HOT NEU
I really don't care what color you use, make best use of what you have confirmed is in the wall and goes to the right places.
Honestly, if it were me, I am quick to tear out and replace wire I am not confident in. Use THHN wire, solid is better for novices. I prefer stranded but I have worked out how to get stranded to go on a terminal screw without rats-nesting. If you have both #12 and #14 wire in your facility, buy #12 as it can sub for #14. Why own two sizes? I own 10 colors of THHN, all #12.
The neutral wire needs special attention since you cut it. You need to find the opposite end of both sides of the cut. It looks like the last guy gave you ample length, so you need to "scooch down" about 4" of length so white comes at least 3" beyond the surface of the wall, on both ends. If there is not enough slack to do that, replace the wire: use the old white to pull the new white through. And don't do that again.
One last thing about conduit: you're free to use any color for hot except white, gray, or green, but you are supposed to be consistent within your facility. I think we're gonna have to let that last one go today because you're trying to reuse/conserve in-place wires, but if you ever buy THHN wire and exploit the marvelous advantage of conduit, make a mental note of that. Gray is an alternate color for neutral, I use it a lot.