@Esa Thank you for the reply. I did look it up, and it refers to the step pulses being too fast.
At the time it happens there are no step pulses being generated, and the wiring has nothing wrong with it.
IN addition to when the pulse signal is plugged in or out, it happens when the motion controller is powered down or turned on - and while the pulse cable is already connected. This could happen at any time but should not normally cause a fault in the drive. And as I explained - the pulse connection is optically isolated, so it should not be to do with any earth problem.
It can be a big problem for example if the camera gimbal is being operated remotely and it’s up on top of a crane or something - then it has to be brought down any time this happens for a reset.
I only have this issue with the IONI drive. I am assuming perhaps there is some disturbance in the pulse line when the motion controller resets after power up, - and which causes some false triggers.
What I need is to know how to desensitise the IONI, perhaps by electrical filtering? The inputs are rated as “high speed” up to 4 mhz, however the actual pulse rate is never more than 1mhz.
Otherwise please - is there was a way to simply disable this fault, as is possible with other faults?