Hey folks. It's me again!

I'm wondering if you could shed some light on a problem I am having with my Arrow 750, Acromatic control, Kollmorgen drives?
The spindle will run and stop just fine up to 750 rpm but if I try to stop it at 800 rpm it just coasts to a stop and I get alarm 39-37. I have checked the resistance of the regen resistor and it checks out ok.
The alarm says to check there is no spindle drift but I don't completely understand the instructions. It says to "set the spindle setup patch on" and I have done this using the cimtrolusa password. It says to programme M3S0 in the MDI, but S-zero doesn't make the spindle spin, obvs. So I'm not sure what else to do here...

The alarm also says it may be necessary to check parameters in the drive unit using motionlink. I have the Motionlink Plus software but was looking for some pointers on what to look for or change...

I really appreciate any help you have to offer me. Thanks!