Is there a "Troubleshooting Guide" regarding warnings and errors?

Okay, right now, the backup has finished, with 27 warnings and 68 errors:

The warnings are of 2 types:

a) Missing remote hash, one of the files is listed as verified with size, but is the wrong size

b) FileAccess Error – this one I can deal with… I exclude this subdir from the backup

The Errors, however, I have no idea how to get rid of:

FailedToProcessFile: Failed to process file duplicati-iXXX.dindex.zip.aes CryptographicException: Invalid header value: 00-00-00-00-00