alt Hacker Newsone thing about discount DIY mini splits: they're sometimes/often the same model, with a hodge podge of similar but not identical components. it can be very difficult to get a repair person to work on these - they stand a lot to lose if they try to operate on it and make it worse. they really prefer consistency, and - they also seem to harbor a bit of a distaste for diy systems. Actually, I was educated by one serviceperson's opinion and by the end of their complaints, the experience cost more than the cash, injury wise. But I think relaying this, has some value, because I suspect it's common.
HVAC techs are in such high demand, they can charge exorbitant rates to install/service, that its not in their interest to service them, or even install them.
It took me a while to find a company to install a mini split I purchased on my own, and I paid $$ for labor. This was only because I didn't have the time.
That said, mini splits are so cheap (sub $500) that its easier to just purchase a new one than repair.