Just realized it has something to do with the artboards. I have to check "All" instead of "Range:" when saving. This creates two files that are exactly the same, except that one of them doesn't have any artboard at all. And the one that does have an artboard gets the annoying "-1" added in the end of the file name, so now I have to delete the pointless file with no artboard and rename the other to get rid of the "-1". Any way to get around this? I have a few hundred files that need to be saved...