Tooway SNR RX weakening

I have Tooway for 4 years now. The location (near Gerona in Spain) is at the edge of three beams (see attachment in the next posting). I am tuned to beam 3.
My Tooway SNR RX signal is very weak. Just around 10.0 dB
When I installed the dish the signal was around 11.3 dB and degraded in 4 years to around 10 dB.
As I wondered if the LNB was deteriorating the provider gave me a replacement LNB a few days ago. But that gave the same SNR RX of around 10.0 dB. The provider now thinks it could be the beam strength from the satelite itself. He is consulting collegues if connecting to another beam could be a solution (which I doubt).

Has anyone encountered a similar problem?
Can the modem be a problem?
Could the cause be something totally different?

Looking forward to your suggestions.

My guesses at possible explanations:

Your dish has moved slightly and is no longer pointed very accurately at the satellite.

The dish surface has corroded or is not clean. The degraded surface absorbs some of the signal.

The feed horn window must be clean and dry with no spiders or damp.

On the downlink to the customer I think there are 4 carriers per beam, comprising 3 carriers of 52 Msps plus 1 carrier of 40Msps, making a total used bandwidth of approx 206 MHz.  Total downlink bit rate per spot is 470 Mbit/s clear sky. ( Some say 475 Mbit/s. )

It would be helpful if someone in Beam 3 could measure the visible carriers on a spectrum analyser. Reports of C/N from other customers at other locations in Beam 3 please..

If all carriers in the beam are low level the satellite output amplifier may have degraded and all downlink carriers in that beam have reduced.

Alternatively if all carriers in the beam are low level, the uplink gateway site may be transmitting all the carriers at reduced power or is suffering severe rain or is mispointed.

If just one carrier is low level then this means an adjustment is needed at the Gateway to equalise the carrier levels.

The beam patterns shown above are notional. Only by precise measurements at multiple ground sites can the actual beam positions be determined. The satellite is not fixed to anything and the pattern of beams is aimed at the earth, probably using tracking on a gateway site.

More of my guesswork here https://www.satsig.net/tooway/ka-sat-system-technical.htm

Eric

A short update:

With the same dish and without doing anything, the signal has improved with about 0.5 dB since a few days. It's now around 10.5 dB.
I wonder if they can reposition the satellite a bit or that they can tweak the beam.

I have also had a Tooway system for almost 5 years, in the Adriatic, also on a Blue circle, but fairly central to the circle.

My signal has dropped over time from 13 to 10 ish.  My Croatian supplier is useless refusing to help in any way!

This week I have lost connectivity.  The RX: SNR is constantly fluctuating as I watch, now between 10.5 and 11.1dB.  Yesteday it was between +6dB and -3.5dB.  I looked to see if I had an owl or something roosting on the dish/tria.  I need to do a re-allign I think.

I've bought a SatLink digital meter to try and align the dish better then the http:/.../install command, but something seems to be going on, beyond my home setup!