Still suffering from a bit of noise or some form of instability, its similar to what I was finding using the Mini Pro to drive a stepper. Checked the PSU and that is nice and stable so when in doubt fall back to what worked to solve the stepper issue I had and that was swap out the Mini Pro for a Nano.

I suspect there is something in the Mini Pro design that makes it a little more susceptible to interference but I guess after a few more cycles we will soon see.

The only other issue it could be is that one of the salvaged caps I used for the R/C circuit has decided to start failing. When i finalise things I may add a few MOV's to the mix