Some feed seem to beempty, but are not!

I'm using a python script to import CSV's from another datalogger. The Feeds that are created upon import are plotting just fine! But some of them state that they are empty:

https://www.dropbox.com/s/16n12ixdvxxfepj/Screenshot%202014-06-18%2019.3...

If I log on to the console of my hosting machine I see that they aren't:

[root@websrv01.my-domain.de /var/customers/webs/ONE/edm.my-domain.de]
292# ls -hl data/php-fiwa/14*
-rw-r--r-- 1 ONE ONE 374K Jun 18 19:15 data/php-fiwa/14_0.dat
-rw-r--r-- 1 ONE ONE  63K Jun 18 19:15 data/php-fiwa/14_1.dat
-rw-r--r-- 1 ONE ONE    0 Jun 18 14:57 data/php-fiwa/14_2.dat
-rw-r--r-- 1 ONE ONE    0 Jun 18 14:57 data/php-fiwa/14_3.dat
-rw-r--r-- 1 ONE ONE   28 Jun 18 15:02 data/php-fiwa/14.meta
-rw-r--r-- 1 ONE ONE    8 Jun 18 19:15 data/php-fiwa/14.npoints

Has one of you seen a behaviour like this before?