[Solved]Unable to stop the spindle fully, stutters 7i96/7i76 Folinn Bd600 0-10v

Thx to all for the help and great suggestions.
I managed to fix it by doing the following:
-Added a ceramic capacitor 0.022uF to the FWD +ve (pin 6) and Gnd (pin 5)
-Added a ceramic capacitor 0.022uF to the REV +ve (pin and Gnd (pin 7)
-Adjusted the OUTPUT_SCALE in the ini as there was a very slight RPM range change (%)

I got the idea from looking at some wiring diagrams where this was suggested for a 0-10V signal.
​​​​​I also added a capacitor to the 0-10v signal at the Mesa board to avoid future issues.

A couple of things I learnt
-There's so much I don't know.
-Ceramic capacitors generally don't have a polarity.
-my oscilliscope couldn't see to the resolution the VFD can hence I couldn't see the noise.
-I probably could have used halscope and turned up the sample rate, hooked up a jumper between the FWD or REV signal and an input and watched it.
-What I thought I'd tested I hadn't.  I've used a number of the same shielded cable, and when I tested pulling the plug on the VFD and Mesa board I must have done the Encoder and VFD board.  Testing it once more (pulling the right cable) stopped the VFD FWD/REV oscillation.
-TIP I've put a different colored tape at the ends of each multi core shielded wire so I can quickly make the cabling association (my VFD is in a control box on the other side of my mill).
 

The 7i76 has spindle enable outputs, which you can link to spindle.0.on in HAL. This, you should be able to simply turn off the VFD if LinuxCNC thinks the spindle is off.