Why would you immediately throw the installer under the bus?
brand new receivers and LNB's fail, Ground blocks fail, Existing home wiring and diplexers fail right out of the box.
I had a service call where the customer lost most of here programing, she was having her house painted and the painters set up scaffolding right in front of the dish!
I have had customers mess with the dish alinement (thinking they could improve it) and loose it all together.
I asked him if he messed with it (helps to know when your troubleshooting it) he said no
The alinement marks were all scratched up, so I know he was lying
And some how its the installers fault because I didn't weld the dish and put up a "no scaffolding here" sign.
That said Loosing one of three sats is usually line of site issues, any trees or other obstructions near the path of the dish (129 is on the right as you look from behind dish)