Hi Thanks for your help.
I checked the linear rails and the wiring again thoroughly but still couldn't find anything out of the ordinary.
I got my head around how to set up UCCNC with my breakout board and I've had it running all week without an issue, the longest it had gone without position loss before was about 8 hours. So I'm still not exactly sure what was causing the problem but at least at the moment it seems to be fixed.