" . . . Still, I'd like to know what those error messages (-35, 19) are. Is there a "glossary" somewhere which might explain them? . . . "
I get those messages from time to time, too. I do NOT have my Time Machine on auto backup. I manually hit "click" when I wish to do a backup with TM on Apple's Time Capsule with Wi-Fi.
The TM will hang in "preparing mode" and then the error message will appear. I click "backup now" again and it rights itself. Backup begins.
On a side note: Even with minimal changes since the last backup, some new backups seem to hit 1.5 GB. It appears that something keeps backing up which does not really need to be (???)
I haven't been too concerned since I have only used 180 of the 1000 GB available on the TC. Still, I do wonder why the 1.5 GB backup happens at times when (I think) there have been very few additions, deletions or other changes to the files and folders which are being backed up.
P.S. I did a System (folder) backup for the FIRST time only. Time Machine preferences are set to ignore this folder on subsequent backups.