File permissions of uploads after upgrade (Network error on Windows client)

Hi there, I just upgraded from 5.1.8 to 6.1.1 successfully. However, since the update files do not get uploaded properly anymore, at least I am getting network errors on the client for libraries changed after the update, plus trying to zip or even only download content from an uploaded folder via the web interface or Windows client results in corrupted files or resp. zip files, all at the same size of 127kB, not containing any files, except for zips with content that is below that size (i.e. files being zipped are below 127kBit altogether).
I looked into the uploaded files within the fs directory via FTP and was able to see that all files have file permissions of 600, so I suspect it to be the reason for this problem. Can anyone point me into the right direction on what to check? Or is 600 the normal routine and something else is amiss?
Running Seafile Pro 6.1.1 on Ubuntu 16.04, latest Nginx, fastcgi in use.

Edit: I let my own user (not seafile) run Seafile, as does the fastcgi/PHP module. Didn’t have any problems with this so far.

Turns out it was rather a problem of an upgraded nginx server running with a false user. The error log of nginx threw out some permission issues which then sorted themselves as soon as I corrected it. Sorry for the false alarm, as it only turned up in conjunction with Seafile specifically I was blind to see beyond its reach!