G0ROZ-3 stopped working on Wednesday morning. Due to problems with the car, I was not able to go to site until today. They have moved the keys for the site from Dorchester to HQ, so I had to go to Winfrith to collect the keys, then to Eggardon Hill, then back to Winfrith and then home.
The problem with G0ROZ-3 was just an error opening the COM port again. A quick re-boot solved the problem.
Looks like I need more UPS power to stop this happening again.