Any ideas on how to fix it? Thank you!
What operation system you are using for full node, Linux, Mac or wiNd0ws?
This is not the first time I see something like this and some files probably got corrupted when power went off suddenly.
Try restarting everything manually and try to reindex the blocks again, if that doesn't work you may need to download blockchain all over again.
Best protection against this would be getting some UPS or running your node on laptop with battery as backup.