Hotbird alignment with zone 1 minidish

Hi
I am trying to align hotbird with my zone 1 minidish and have found some transponders have better snr with dish moved slightly to the left and some transponders are stronger with the dish moved slightly to the right is this normal I thought they would be all stronger in one set position?

Is a zone 1 dish big enough for hotbird I am in West Wales? Some transponders I can only get 57% and drop out in rain.

Would appreciate some advice or if there is best transponder to tune dish to?

Thanks