PDF File is shown as 0 bytes, but can be downloaded via web-interface

I have a problem with one file in an encrypted library. In my local synchronization, that file is 0 bytes. I’ve known this for quite a while, but always thought that somebody just uploaded it this way (or it broke during upload or whatever). But now I noticed that in the web interface (after typing the decryption password), the file is also shown to have 0 bytes – but I can open and download it just fine. It is a PDF file (scanned image) and indeed it is about 1 MB large.

I’m seeing just now that in fact, there are two very similar files in that directory with the same problem. The other one is about 600 KB (but shows as 0 bytes).

As far as I know, no such problem exists in any of our other libraries (whether encrypted or non-encrypted).

seaf-fsck outputs only this:

Starting seaf-fsck, please wait …

[12/14/18 21:38:40] fsck.c(593): Running fsck for repo …
[12/14/18 21:38:40] fsck.c(413): Checking file system integrity of repo …(…)…
[12/14/18 21:38:40] fsck.c(657): Fsck finished for repo …

seaf-fsck run done

Done.

Any ideas what might cause this, or I might go about debugging it?

Thanks,
Markus