On my ride this morning I noticed that although I was on a section of road that climbs gradually for several kilometres, the elevation field reading on my 1030 data screen was gradually decreasing, and then when I next looked at the elevation field a kilometre or two later, it was back up to where I would have expected (this is a road that I ride quite often). When I finished and uploaded the ride to Garmin Connect, the elevation graph shows that I appear to have climbed a vertical wall at about that point. Here's a screen dump of the graph. Apart from this anomaly, the elevation graph for the rest of ride corresponds to reality. The 1030 was on a mount on my handlebars and there was nothing at any time obstructing whichever hole the barometric altimeter uses for its readings - the ride was dry thoughout:
This is a new 1030 that was supplied about a week ago as a replacement for one with the blue screen halo.