Answering the second question first because it's easier:
We have wye'd PWM signals to at least two motor controllers in the past when we wanted to control them from the same signal. We saw nothing against it in the rules, and the inspectors either didn't notice or didn't see it as a problem. AndyMark actually sells a
cable for just this purpose, though I believe we made all our own.
Back to the first:
- Did you calibrate the Talon SRs?
- Have you tried to isolate the issue as being a talon vice a 'RIO vs a motor problem?
- You can check whether it's a motor problem by measuring the voltage across the talon's output terminals.
- If you don't have an o-scope, the easiest way to check the talon is to swap two talons at both the PWM and motor output ends, and see if the problem tracks the talon or the signal.