I've built a PhantomX Hexapod mkIII and have a strange problem with it. Either all the 18 dynamixels are detected or none. I've added a bluetooth serial port to the standard build and this just confirms it.

Sometimes it powers up and moves after detecting all 18, then stops, and debug checks indicate no dynamixels detected again.

Surely a loose cable would just affect one string no?

It's a standard build based on the Arbotix-M board with the AX/MX power expander. I'm running it from a 12v 10a PSU for now.

Any tips on this type of fault?

Thanks in advance.