Yes 12224 is Dishnet, but the question is why only when the meter is attached. I will throw a theory out there that I just whipped up.
That meter does have its own internal power supply for the LNBs. The power supply of the meter must be doing a better job (less cable resistance between it and the LNB) than the STB on its own. The LNB with full juice is performing better.
I get 12224 signal without the meter on the linear LNB. But it is scrambled and useless to me.
It makes me curious if I should apply separate power to my LNBs way in the back yard to see if they will do a bit better on the weaker signals.
If you replace your present RG6, that now has a copper clad steel #18 conductor, with a different RG6 that has a solid copper #18 conductor, you too can have the useless 12224 signal without the meter installed inline.