Well... that's a crazy little BoB you have there... quite unlike any I've seen, but that what keeps life interesting. Yes, the manual for it (such as it is) describes the supply as a single 5Vdc supply, possibly USB sourced (though you identify that you're driving with a 5V/5A supply - nothing wrong with that.

In trying to understand what you described as spurious triggers from the limit switches and e-stops... the problem is that from those photos in your profile (nice and reasonably clear - thank you!) everything is obscured by the display mounted to the board. What I was curious about was whether the inputs are isolated (Opto isolator/opto coupler) or just hard-wired... and of course the display covers all of that detail - and the manual I found online is less than useful!)

Surrey is sufficiently far away to make me start to lose interest in this - I'm inclined to suggest that if you was to look under the display, near the terminal blocks for the input limit switches to see if you can see 5 Opto-isolator devices (google them for an image) - if these aren't visible on the board then I'd personally be thinking of replacing the BoB with a cheap Chinese (£6) parallel BoB... just to get to a configuration that we're mainly familiar with.

If you're adventurous enough to lift the display from the BoB and get another photo of the main PCB, that could be useful to examine further. Where I am with this is - if your BoB doesn't have Opto-isolated inputs, and you're suffering noise, the replacement BoB, and the cost therein, versus the effort of trying to diagnose (and resolve) a BoB without isolated inputs is a no brainer for me. A good image of the components fit to the main board would be good.