Tvheadend

Hi,
I'm using a Digital Device Cine S2 V7 PCIe DVB-S2 card with TVHeadend.
This always worked great with an Universal LNB on Debian 8 with TVHeadend 4.0.

Some days ago I upgraded my sat installation to Unicable 2 (JESS). This works great on all receivers in my house. But TVHeadend (or Debian, or the card) didn't like it.
Yesterday I did a clean install of Debian 9 stretch and installed TVHeadend 4.2 stable.

After also installing the drivers for the card I get both tuners listed (STV0910 #0, STV0910 #1). For the TV adapter config please see the 2 tuner screenshots attached below.

When I add a mux with correct values according to ASTRA 19.2E and force a scan the tuner is tuning to the correct frequency and I get no errors logged on TVH or dmesg. I see a Signal Strength but no Bandwidth or other values except "Uncorrected Blocks" which is increasing to a high number in a few seconds (see tuning screenshot).

On both tuners the sat cable is linked and when I use a cheap receiver I get full signal there. Just not with my pc.

Because I'm using Unicable I also can't use w_scan or other tools to test if the card is working as expected.
Privileges for /dev/dvb are root:video, user hts is in group video and can access them.

Do you have any ideas how I could get this working?

Sven