nobody thinks you are lying, why you don't want to accept that the tuner might be defect one
there is no reason to not believe you have an issue, but it has nothing to do with the AGC, because there isn't any AGC measurement available with latest tuner HW.
You can check this in the original image in your flash, there isn't any AGC field anymore.
It looks to me you are lost in the image scene a little bit.
If you don't like the original image you can install the GeminiProject plugin on it to expand the functionality.
Or you can use image of another team and you can install it in the flash if you don't want to use the multi-boot plugin.
You can choose either from the Open-Aliance images or from the ones based on the original opendreambox image like Merlin, Oozoon and others.
hope it helps
BTW. your last message is really not well understandable, sometimes less words and shorter sentence make more sense