Tvheadend

Hy,
I want to replace my Mediaportal TV Server with Tvheadend and unfortunately i am not able to solve my problem...
The whole hardware chain is definitely error-free, because it runs with the Mediaportal TV Server for years without errors.
On the same computer I try to get Tvheadend running.

Here the problems seem to start already with the channel search, because not all channels are found (~111 Muxes and 127 Services on 19.2E Astra).
Found services are working sometimes and sometimes not. Sometimes it helps to disable 3 of 4 adapters.
Then again it works with 4 active adapters and then again it doesn't, even if only one adapter is active!
Tvheadend log:

Loglevel debug : enabled
2019-03-09 17:37:58.791 mpegts: 11362H in DVB-S Network - tuning on STV0910 #3 : DVB-S #0
2019-03-09 17:37:58.799 subscription: 0012: "HTTP" subscribing to service "DVB-S Network/11362H/ZDF HD", weight: 100, adapter: "STV0910 #3 : DVB-S #0", network: "DVB-S Network", mux: "11362H", provider: "ZDFvision", profile="pass", hostname="192.168.1.30", client="VLC/3.0.6 LibVLC/3.0.6" 
2019-03-09 17:38:08.807 subscription: 0012: service instance is bad, reason: No input detected
2019-03-09 17:38:10.807 webui: Couldn't start streaming /stream/service/95ddcbfbfe9bbcf3298d6c4154d834d4?ticket=EED5AD8CE7D89188B6227079CFF70120CE168FDF, No input detected
2019-03-09 17:38:10.810 subscription: 0012: No input source available for subscription "HTTP" to service "DVB-S Network/11362H/ZDF HD" in mux "11362H in DVB-S Network" 
2019-03-09 17:38:10.810 subscription: 0012: "HTTP" unsubscribing, hostname="192.168.1.30", client="VLC/3.0.6 LibVLC/3.0.6" 
2019-03-09 17:38:10.825 http: 192.168.1.30: using ticket EED5AD8CE7D89188B6227079CFF70120CE168FDF for /stream/service/95ddcbfbfe9bbcf3298d6c4154d834d4
2019-03-09 17:38:10.827 mpegts: 11362H in DVB-S Network - tuning on STV0910 #3 : DVB-S #0
2019-03-09 17:38:10.834 subscription: 0013: "HTTP" subscribing to service "DVB-S Network/11362H/ZDF HD", weight: 100, adapter: "STV0910 #3 : DVB-S #0", network: "DVB-S Network", mux: "11362H", provider: "ZDFvision", profile="pass", hostname="192.168.1.30", client="VLC/3.0.6 LibVLC/3.0.6" 
2019-03-09 17:38:20.827 subscription: 0013: service instance is bad, reason: No input detected
2019-03-09 17:38:22.828 subscription: 0013: No input source available for subscription "HTTP" to service "DVB-S Network/11362H/ZDF HD" in mux "11362H in DVB-S Network" 
2019-03-09 17:38:22.828 webui: Couldn't start streaming /stream/service/95ddcbfbfe9bbcf3298d6c4154d834d4?ticket=EED5AD8CE7D89188B6227079CFF70120CE168FDF, No input detected
2019-03-09 17:38:22.831 subscription: 0013: "HTTP" unsubscribing, hostname="192.168.1.30", client="VLC/3.0.6 LibVLC/3.0.6" 

Kernel messages with 'dmesg | grep DVB':

[ 2.107348] ddbridge 0000:01:00.0: Port 0: Link 0, Link Port 0 (TAB 1): DUAL DVB-S2
[ 2.222486] ddbridge 0000:01:00.0: Port 1: Link 0, Link Port 1 (TAB 2): DUAL DVB-S2
[ 2.223111] dvbdev: DVB: registering new adapter (DDBridge)
[ 2.223112] dvbdev: DVB: registering new adapter (DDBridge)
[ 2.223112] dvbdev: DVB: registering new adapter (DDBridge)
[ 2.223113] dvbdev: DVB: registering new adapter (DDBridge)
[ 2.223113] dvbdev: DVB: registering new adapter (DDBridge)
[ 2.223113] dvbdev: DVB: registering new adapter (DDBridge)
[ 2.272696] ddbridge 0000:01:00.0: DVB: registering adapter 0 frontend 0 (STV0910)...
[ 2.276452] ddbridge 0000:01:00.0: DVB: registering adapter 1 frontend 0 (STV0910)...
[ 2.301773] ddbridge 0000:01:00.0: DVB: registering adapter 2 frontend 0 (STV0910)...
[ 2.305310] ddbridge 0000:01:00.0: DVB: registering adapter 3 frontend 0 (STV0910)...
[ 6.972753] ddbridge 0000:01:00.0: DVB: adapter 3 frontend 0 frequency 0 out of range (950000..2150000)
[ 6.979576] ddbridge 0000:01:00.0: DVB: adapter 2 frontend 0 frequency 0 out of range (950000..2150000)
[ 6.984563] ddbridge 0000:01:00.0: DVB: adapter 1 frontend 0 frequency 0 out of range (950000..2150000)
[ 6.989471] ddbridge 0000:01:00.0: DVB: adapter 0 frontend 0 frequency 0 out of range (950000..2150000)
[ 7.814882] dvb_ca_en50221: dvb_ca adapter 4: DVB CAM detected and initialised successfully

I have set up following systems, always with the same result:
- Ubuntu Server 18.04.02, integrated DVB kernel driver, Tvheadend unstable 4.3-1281
- Debian 9, DD driver v0.9.36, Tvheadend unstable 4.3-xxxx
- Debian 9, DD driver from GitHub (Commit 360182 from 18.01.2019), Tvheadend stable 4.2.8-14

Hardware infos:
- DDOctopus Twin CI & DuoFlex S2 V4 & DuoFlex S2 V4A
- The SAT connectors of the two DuoFlex are wired to a Multiswitch which is powered by a 4-port LNB.
- Intel Core i3
- ...

Has anyone successfully used a DD DuoFlex S2 with Tvheadend?
I would be very happy about tips and suggestions to solve my problem!