Encoder Conundrum

[Hitchhiker 42]

So, our team has had season-long difficulties with our encoders on our drive train (This one).

Consistently, at first, we had our left encoder working and the right one not working. We worked around this, using only the left side for distance. However, we decided to fix this in the off-season. We replaced both encoders (left & right) for brand new ones. We also tested the wires for shorts and continuity where they should/shouldn't be. All fine. The problem persists.

Our next step was to try to connect them directly through the Talon SRX with the little expansion board for wire --> ribbon cable. Now, the right encoder started working and the left one didn't. Thinking this was the wires, we replaced & tested all four parts (2 ribbon cables & 2 encoder wires). No difference. The problem persists with the left side now.

We are going to try to switch to magnetic encoders, but it's still an interesting conundrum as to why all of this happened. Why was one working, and then they switched?

Any advice is helpful, Thanks!