I was out around bulls bay this weekend with the bimini top up and I kept getting errors on my Garmin gps. I would loose a signal for a while sometimes. Will an external mounted antenna mounted right beside the unit really make a difference?
I had a Garmin 182C with a built in antenna and it worked fine anywhere I put it including the lower helm of my boat with a flybridge.
I doubt your problem is with something blocking the antenna, but just to be sure, the next time you get an error, move it to where it gets a clear view of the sky and see if the error goes away.
Is your unit even designed to accept an external antenna?
It’s a 441s and can take the GA30 puck. I have never had a problem, but I was going down the ICW near Buck Hall and took a creek to head to Bulls and the map kept me on the ICW for about 15 seconds. Then later on down the creek the speed stuck and it put me in the marsh on the map even though I was in the channel.
I had a similar issue with a garmin handheld once. Seems the “WAAS” had inadvertently gotten “enabled”. Called customer support because the unit would continuously lock up and quit navigating. Turned WAAS off and never had another issue.