I tried to resync now, and had to pass the -c flag to make sure it checked the cheksums to see if they should be updated. Then it worked. Looks like that does not affect the after-transfer checksum check though, so that's good (from documentation):
Note that rsync always verifies that each transferred file was correctly reconstructed on the receiving side by checking a whole-file checksum that is generated as the file is transferred, but that automatic after-the-transfer verification has nothing to do with this option's before-the-transfer lqDoes this file need to be updated?rq check.
How would I achieve that? With cron?