it seems that the watch defaults to trying to autodetect your max heart rate which makes a mess of ones heart rate zones. i know my max is 194 (from a hike last year) and my previous watches had set it to 192, but for some reason, the 955 Solar thinks my max is 180. i reset the max the other day but didn't realize there was an autodetect setting to disable.
anyway, i hope this is helpful for others.