I’m really sorry to hear about the print stoppage issues. I absolutely understand how frustrating that can be.
There are a lot of aspects to SLA printing that make restarting after an indefinite pause pretty tricky, and if the printer loses power completely, the printer won’t know how long it’s been off. Things like heat loss, resin shrinkage and more all come into play.
This isn’t an excuse, just an explanation. Like I said, it’s really annoying to lose progress like that. As suggested, a UPS is a great thing to have to prevent this sort of issue from affecting your work in the future.