I've had the same issue from time to time. I'm not certain the exact setup I have, but, I believe I have a SWM-16 switch. I have 4 coax lines coming out of my dish into this switch, then, although all of the lines are not in use any longer, there are what look like 4 way splitters coming from wires coming out of the SWM switch. These wires go to an HR-23, HR-24, & and HR-34 which gives me 9 tuners as well.
Sometimes, after a "power glitch" or rain issue, I'll get a 775 error. In my case, a "reboot" of the power inserter by giving it a power cycle has fixed the 775 error.
My SWM Switch and Power Inserter are in the drop ceiling of my basement and not in the attic.
Is the extreme heat of this environment a problem for these devices?