AXBB charge pump fault

[Doddy]

It is behaving slightly different this time though in that the relay doesn't switch on until the charge pump is active. The problem comes when the reset or estop is tripped. The charge pump led switches off but the relay stays active ( the relay led stays lit but dimly when the charge pump output should be inactive?)

So the LED on the AXBB is off, but the relay remains energised and another LED on the relay is on/dim?

That suggests the FET is conducting, when it should be off. No disrespect to John but worth a visual around the replacement FET and a wipe down with IPA if there's any flux residue, but I doubt that will resolve anything (the gate is tied to ground via resistor so can't really believe any parasitics will be able to draw the gate high). Worth measuring the voltage on the gate of the FET (report here) and the voltage ACROSS the relay coil when it should be off - my guess is you'll have a few volts there and if the voltage on the gate is essentially zero then, with the circuit as shown, it can only be the FET. Replace again. If it fails again then replace with a bigger bugger. Or haywire the 74HC14 output to the adjacent FET and use that output instead.