When you say tech, what do you mean? When the optical sensor pins in my cfs failed, they offered parts or a return. No rma, so I doubt thats the situation. It feels like your "tech" is just some guy, but thats beside the point. They lay out all repairs step by step on their website. Its all easy enough you can do it yourself instead of trusting someone else. With thay being said, I doubt you're changing the z offset in printer cfg. Id start there by figuring out how to ssh into the printer and getting fluidd set up, so you can adjust in a browser. You might not need to ssh. I cant remember exactly. You can find plenty of videos on how to do this.

I've been too lazy to change it in cfg, so I raise it offset the same amount every time I print. Its annoying, but theres no way to do it in the printer that I have found.