poodle guy

I have a 2016 Denali HD that has a problem where the GPS screen wanders and will not lock in. It comes and goes but I was able to get it into the dealer while it was happening. The got some codes, I don't have the code numbers, that indicated low voltage at the fuse block. They also said there was a service bulletin out about it. I searched for bulletins and don't see anything specific to the 2500 Denali. Not that I don't trust the dealer but ... The plan is to change out the fuse block ( $300.00+) and if that isn't the fix, replace the radio ($600.00+) Just wondering if there is anyone here that has had the same issue or some advice.