Tvheadend

Hi everyone,
I'm trying my very best to get TVH back up running, after introducing a separated network... Prior TVH was using the FritzBox 6591 integrated DVB-C-quadtuner from the same network (10.30.0.0/16). Now, the FritzBox is in a separated network 192.168.178.0/24. The RasPi, running TVH, is still in 10.30.0.0/16.

Problem is: TVH can't stream, despite ffmpeg or another client in the same 10.30.0.0-network can.

Here is the configuration:

FritzBox 6591: 192.168.178.1
Gateway: 10.30.5.1 -> gets IP 192.168.178.4
TVH on RaspBi: 10.30.4.12

Version of TVHeadend: HTS Tvheadend 4.2.8-36
Running on what OS and version? Raspbian GNU/Linux 9 (stretch) Linux berry 4.19.66-v7+ #1253
Package that came with the OS or something you compiled yourself? https://apt.tvheadend.org/stable
Adapter/tuner chipset or make/model?: FritzBox 6591
Detailed description of problem:

TVH start parameters: TVH_ARGS="--satip_xml http://192.168.178.1:49000/satipdesc.xml"

What actually DOES work :
1. starting a stream from VLC, e.g. rtsp://192.168.178.1:554/?freq=330&bw=8&msys=dvbc&mtype=256qam&sr=6900&specinv=1&pids=0,16,17,18,20,5100,5101,1170,1176,2171,2172,5102,5103,5104,5105
2. starting a stream from rasbpi with ffmpeg: /usr/bin/ffmpeg -loglevel fatal -i 'rtsp://192.168.178.1:554/?freq=330&bw=8&msys=dvbc&mtype=256qam&sr=6900&specinv=1&pids=0,16,17,18,20,5100,5101,1170,1176,2171,2172,5102,5103,5104,5105' -vcodec copy -acodec copy -f mpegts -tune zerolatency pipe:1
3. adding a stream to TVH as IPTV with pipe:///usr/bin/ffmpeg

What is NOT working :
Scanning muxes/streaming from TVH.

Adapters
https://ibb.co/Kj26FDj

Network Settings
https://ibb.co/Gf6Rn0j

Mux after Scan
https://ibb.co/GWdpX1t

DVB-C Tuner 1 Config
https://ibb.co/5R79WH9

Status from FritzBox during forced scan of freq 330 MHz

Syslog is attached, excerpt:

Aug 18 13:07:12 berry tvheadend[874]: httpc: 0051: RTSP/1.0 answer 'RTSP/1.0 200 OK' (rcseq: 4)
Aug 18 13:07:12 berry tvheadend[874]: httpc: 52 54 53 50 2F 31 2E 30 20 32 30 30 20 4F 4B 00 RTSP/1.0 200 OK.
Aug 18 13:07:12 berry tvheadend[874]: httpc: 0A 43 53 65 71 3A 20 34 0D 0A 53 65 73 73 69 6F .CSeq: 4..Sessio
Aug 18 13:07:12 berry tvheadend[874]: httpc: 6E 3A 20 31 30 38 0D 0A 52 54 50 2D 49 6E 66 6F n: 108..RTP-Info
Aug 18 13:07:12 berry tvheadend[874]: httpc: 3A 20 75 72 6C 3D 72 74 73 70 3A 2F 2F 31 39 32 : url=rtsp://192
Aug 18 13:07:12 berry tvheadend[874]: httpc: 2E 31 36 38 2E 31 37 38 2E 31 2F 73 74 72 65 61 .168.178.1/strea
Aug 18 13:07:12 berry tvheadend[874]: httpc: 6D 3D 39 34 00 0A 0D 0A                         m=94....
Aug 18 13:07:12 berry tvheadend[874]: httpc: 0051: finishing
Aug 18 13:07:21 berry tvheadend[874]: mpegts: table: mux 0x1b22948 destroy sdt 40/F8 (64) pid 0011 (17)
Aug 18 13:07:21 berry tvheadend[874]: mpegts: 330MHz in DVB-C - close PID 0011 (17) [20/0x72304798]
Aug 18 13:07:21 berry tvheadend[874]: mpegts: table: mux 0x1b22948 free sdt 40/F8 (64) pid 0011 (17)
Aug 18 13:07:21 berry tvheadend[874]: mpegts: table: mux 0x1b22948 destroy nit 00/00 (0) pid 0010 (16)
Aug 18 13:07:21 berry tvheadend[874]: mpegts: 330MHz in DVB-C - close PID 0010 (16) [16/0x723150a0]
Aug 18 13:07:21 berry tvheadend[874]: mpegts: table: mux 0x1b22948 free nit 00/00 (0) pid 0010 (16)
Aug 18 13:07:21 berry tvheadend[874]: mpegts: table: mux 0x1b22948 destroy cat 01/FF (1) pid 0001 (1)
Aug 18 13:07:21 berry tvheadend[874]: mpegts: 330MHz in DVB-C - close PID 0001 (1) [16/0x723103b8]
Aug 18 13:07:21 berry tvheadend[874]: mpegts: table: mux 0x1b22948 free cat 01/FF (1) pid 0001 (1)
Aug 18 13:07:21 berry tvheadend[874]: mpegts: table: mux 0x1b22948 destroy pat 00/00 (0) pid 0000 (0)
Aug 18 13:07:21 berry tvheadend[874]: mpegts: 330MHz in DVB-C - close PID 0000 (0) [20/0x7230c500]
Aug 18 13:07:21 berry tvheadend[874]: mpegts: table: mux 0x1b22948 free pat 00/00 (0) pid 0000 (0)
Aug 18 13:07:22 berry tvheadend[874]: mpegts: 330MHz in DVB-C - scan no data, failed
Aug 18 13:07:22 berry tvheadend[874]: subscription: 0167: "scan" unsubscribing
Aug 18 13:07:22 berry tvheadend[874]: mpegts: 330MHz in DVB-C - close PID tables subscription [0042/0x7230b810]
Aug 18 13:07:22 berry tvheadend[874]: mpegts: 330MHz in DVB-C - stopping mux

Any ideas?

Thank you very much!