Put it briefly: the key “OrcX01_XX” that holds your latest Rexxar Campaign progress is likely deleted/lost/corrupted, if you don’t keep even one save at main map and you can’t recover the key file back, then I’m afraid you have to replay the whole Act 1.
About the “sometimes it doesnt load any characters and is just stuck” thing, I guess you probably loaded those “OrcX01_XX” instead of normal saves.