I moved the feature discussion here: File Integrity Verification
In this thread I really want to dig deeper into the things I am experiencing. Let me elaborate on the specifics on one of these occasions:
On of the affected folders is shared with an external company that receives PDFs from us via Syncthing for further processing. We just drop a PDF into the synced folder and do not touch it afterwards.
The company then raised this issue with the corrupted file and sent it back via email.
The file had the correct name and size. This information must have been transmitted via Syncthing, as there was no other means of communication for this. But the file was only filled with zeros.
Is it possible that the program, that initially placed the PDF in the folder, first allocated the needed size on the filesystem (with zeros) and Syncthing picked up the new file before it was actually written to disk, synced a file full of zeros and then did not pick up the actual write afterwards?