There are a number of possible causes. The first thing that comes to mind is a bad shield connection at a connector. Other possibilities include a tree or other obstruction between the dish and the satellite, or a bad multiswitch or LNB, or even a powered multiswitch has been known to cause problems.
The fact that the problem occurred after some renovations is significant. The overwhelming odds are that a connector was scrogged in the process. Check them carefully.
If that fails, let's 'walk the problem out'. You mentioned that you have a WB68 multiswitch. The 'slimline' HD dish has 4 outputs; you mentioned a second DVR. Do you have other receivers? What are the signal levels on those? If the problem only occurs on the cables to the HR20-700, try moving those cables to other outputs of the WE68
If the problem occurs on all receivers, what happens if you hook a receiver directly to the coax from the dish?
Do you have another (powered) multiswitch hooked to the WB68? That can cause problems.
There's a difference between needing help, and just being plain ole' lazy.
"You cannot teach a man anything. You can only help him find it for himself." Galileo Galilei (1564-1642)
HR20-700 with 2 TB, HR22-100, HR22-100, HR22-100, HR23-100 all running 0x5cd and networked.