Thank you for the explanation.
Please check the older Dual LNB.
Has the white plastic cover fallen off?
I've seen a rash of these the past year, and eventually the water gets in and destroys it.
If the cover is still on the LNB, do you have trees growing that may be interfering with the signal?
If the issue is not trees, and the cover is still in place, maybe the LNB itself is just getting old and starting to fail.
I've seen older Bell and Shaw LNB's that are failing, giving weak signal strengths.
So, as I said before, if you want to install the new Triple LNB, then make sure you have good signal using Ch.299 (at least 80) with the older Dual LNB first.
Then exchange the LNB's without moving the dish.
Call Shaw, tell them you've installed the new Triple LNB, and they will send the correct v-codes and maps to your receivers.
It may take 15 mins for the receivers to start working again after Shaw has Refreshed your receivers.
P.S. I just thought of something else.
Do you have a Model 60E dish, or a Model 75E dish???
There two different Triple XKu LNB's, one for the Model 60E and one for the Model 75E.
You MUST use the correct one.