[GeeTwo]

A I understand things it shouldn't, if things are wired correctly.

If you don't get some more specific guidance from Omar or someone else at CTRE, check your encoder cables and breakouts to make sure everything is connected where it should be (including under a bit of flexing) and disconnected where it should not be connected (again, including under flexing). Also, check that you are using an encoder (not analog) breakout.

Also, double check your code to make sure you aren't giving the SRX conflicting signals. Perhaps you forgot to comment out something in your encoder code, and your remnant encoder code and your new constant voltage code are fighting each other.
If you don't find any issues, if you post your code here, or provide a link to your github or other code repository, there are several here on CD who will look your code over for this sort of thing.

Finally, if things still don't work, post the state of your SRX's diagnostic lights when it jitters; that may be illuminating.