limits switch activated randomly

Also use shielded cabling on all inputs, all shields grounded properly, no machine cables going parallel with the torch cable, computer and electronics as far as possible from the plasma and torch cable. All this is paramount to a functioning plasma cutter, especially if you have a HF/HV start plasma (high frequency, high voltage). If using a cheap break out board, they need to have pull up resistors on all inputs, if they do not already have them, on some you need them at a lover value even if they do have them ( some cheap BOB use 10K pull ups and that is way to much for plasma functionality, they need to bee 1K or even 470Ohm ) otherwise they tend to get messed up as soon as the torch fires.
Regards,
Tom