Tvheadend

I have issues with a grabber I wrote myself for Chinese TV.

It is located at /usr/local/bin/tv_grab_cntv
I can select it in Internal Grabbers, the channels are recognized.
I also set the EPG source in the channel list to the corresponding xmltv source.

However, while the channels are recognized and selectabled (with correct chinese names) no programme information is gathered from the XML.

Dec 02 22:40:29 [tvheadend] /usr/local/bin/tv_grab_cntv: grab /usr/local/bin/tv_grab_cntv
Dec 02 22:40:37 [tvheadend] /usr/local/bin/tv_grab_cntv: grab took 8 seconds
Dec 02 22:40:37 [tvheadend] /usr/local/bin/tv_grab_cntv: parse took 0 seconds
Dec 02 22:40:37 [tvheadend] /usr/local/bin/tv_grab_cntv: channels tot= 24 new= 0 mod= 0
Dec 02 22:40:37 [tvheadend] /usr/local/bin/tv_grab_cntv: brands tot= 0 new= 0 mod= 0
Dec 02 22:40:37 [tvheadend] /usr/local/bin/tv_grab_cntv: seasons tot= 0 new= 0 mod= 0
Dec 02 22:40:37 [tvheadend] /usr/local/bin/tv_grab_cntv: episodes tot= 0 new= 0 mod= 0
Dec 02 22:40:37 [tvheadend] /usr/local/bin/tv_grab_cntv: broadcasts tot= 0 new= 0 mod= 0

The created xml file is attached (normally returned on stdout).

Do I miss something in the xml? According to the xmltv DTD, only the title subelement and the channel and start attributes are required.

I am using Tvheadend 3.4.27 (Gentoo)