this is not strictly a syncthing issue, but something that afflicts most mac users of syncthing badly.
Time Machine seems to back up the Library/…/Syncthing/index directory, which in my case is about 1GB. and it does like to do this on the hour every hour.
This needs to be turned off somehow. unfortunately, adding the folder to my time machine exclusion does not work. grrrr…
Seems weird. Usually what I exclude from TM Backups will stay out of backups.
If you run:
sudo mdfind "com_apple_backup_excludeItem = 'com.apple.backupd'"
you should be able to check the excluded path.
My 2 cents. Regards,
Update: I kinda reproduced your TM configuration excluding the
~Library/Application Support/Syncthing/index-v0.14.0.db folder and I can confirm it’s correctly excluded form my backups.
Using Mac OS Catalina 10.15.6.