Thanks for the suggestions guys!
Ok so, I tried two things out and neither had any effect:
Still on firmware 2.8.0, I changed out the receiver for a 4649T unit.
Then, I upgraded the firmware to 2.8.1.4 and tried both the 4649T and 4651T. (I’ve made my own plugs to connect the receivers to the FBL taking care to put the pins in the right locations relative to the uSpirit’s pin polarity)
The strange servo behavior was still present no matter what I did. It really feels like all the channels and inputs are just scrambled
Any other thoughts? Unfortunately I don’t have another micro spirit to compare against. I’m having a hard time telling if this is a software or hardware problem, but as I mentioned previously I’ve been using spirit units for over three years without ever seeing anything like this.
Video of one of the servos going up when I move the stick up as well as down:
https://imgur.com/gallery/zGNOd5H