Just one idea. Have you tried setting the RF modulator to an alternate frequency? It may be co-channel interference
Strangely enough I dont use the RF modulator but did have a slight interference pattern on my TV when using a 21pin scart cable. (This pattern appeared if the dreambox was on and recording a program to the hard drive and I was watching TV.)
This disappeared when I retuned the RF modulator to UHF channel 21 (not used in my area)
also set sound subcarrier to 6MHz and not 5.5MHz

Hi, your antenna is using a monoblock LNB (6.2 degrees separation) and you are aligned to Astra/Hotbird.
This is also the same configuration as my antenna.

Heres how to solve it:-
You should be able to scan one satellite without errors, in my case this was Astra at 19E.
When you try to scan hotbird you will probably find the signal is too weak to lock and you get BER errors.
I'm using a DB7020 wih Gemini 2.7 image these instructions are for gemini:

Go to setup, service searching, manual transponder scan.
At this screen you may find (as I did) that the agc signal is weak and not locked and you have BER errors.
Find a list of frequencies, i.e. google + lyngsat and then manually input a frequency , polarity and symbol rate. Once this has been entered press start scan, it should find some channels, repeat this process on another frequency and scan a few channels.
Then return to service searching and hopefully you should be able to do an automatic transponder scan.

I think that the satellite configuration starts at one end of the band where there is a weak or no signal and hence automatic transponder scan fails; manually inputting a few channels should correct this.
Hope that helps.