/data/data/org.fdroid.fdroid/files keeps all installed apk files

Since middle of the June F-Droid keeps piling up apk files in /data/data/org.fdroid.fdroid/files/. I already have 16 apk files with names matching regular expression ^install-{1,2}[0-9]{9,10}.apk$ These files occupy 60MB in total. I suppose these files are apks that I have installed in past two months.

This is not expected behaviour. I've set cache duration in F-Droid settings to 1 hour and still I get historical stuff that eats up space. Is it safe to delete these files?