I've had my G5 for about 5 months now and use it every day. I have only seen this error message occasionally when turning power on, with both the "Michigan" R11P firmware, and the newer firmware Unication released 1/2018 ("R02?"). My radio is currently into Unication for the Phase II upgrade so we'll see how that firmware behaves once I get it back.
Each time I see the error, I just hit the 3-finger button combo (hold two buttons on left side of pager plus the playback button on top for a few seconds) and that clears it, it reboots and is back to normal.
From my experience, this isn't a huge deal and only happens on less than ~2% of powerups. I have kind of chalked it up to it being a (relatively) low cost unit from Taiwan compared to anything else that can reliably receive simulcast traffic......a startup glitch once in a while might be par for the course. Have never seen this happen after it is up and running, as such I consider it a minor issue.