Found this and it worked. Had to switch to the classic view of connect:
I noticed in the Garmin Connect site that when I looked at the measurements in the Garmin Connect site that there was a measurement record that was dated more than a year from now.
When I deleted this record, the problem went away, so I can only assume that the system was simply looking at the most recent weight measurement and it wasn't able to identify it as being incorrect because it was in the future.