Bill are you using an SK-3005 with SWM8 and OP using a ground mount SL3s? Might be apples and oranges.
OP's SWM signals are low. I don't know the relationship between the SWM readings and bird readings. I'm sticking with bent, not aligned, bad LNB or bad cabling. Without knowing it is aligned and getting a meter in the mix, really can't help much.
For a quick test, I bagged my LNB. Zippo on ALL readings. So, taking into account Bill's findings and mine, good dishes and LNB's w/o signal gives all zeros. I'm thinking a bent or misaligned dish would then do the same. OP has SWM readings. Bad LNB?
Edit: Or bad cabling. Connected but not good enough to get 21v to the dish or signal back down?