commit diffs not shown

i converted some repositories svn to git and when pushing such repos to gitlab-ce (8.5.x, 8.6.x) it shows commit info, but diffs render just:

Showing 0 changed files with 0 additions and 0 deletions

some commits show diff, most of them not...

i've tried reinstalling gitlab, doing cleanse, recreating vm, nothing helps

also there's nothing in logs (gitlab-ctl tail) that would indicate what the cause could be. i'm really helpless here, tried ask several times from irc, gitter, nobody answers :(

if i do git show in the bare repo dir from commandline, the commit diff is shown properly