I´m wondering if there is a way to delay the synchronization process for an specific file until it hasn’t changed for an specific amount of time (e.g. the modification time for this file is from more than four hours ago)
I usually work with a small set of files for a few hours and I don´t want that they get synchronized until I´m done with them, for avoid sending the file multiple times while I´m working with them and “pollute” my versioning on the synchronized device.
Or is this already taken care with the “scan interval” (no way that a file gets resend in less than “scan interval” seconds?
Unless you’re using something like syncthing-inotify: correct. Syncthing will scan you files once every “scan interval” - if the scan interval is set to 2 hours, Syncthing will scan your files once every 2 hours.
Please note that this error itself should be harmless. Syncthing will keep trying to scan the file until succeeded. It may, of course, use some resources in the process.