Not a direct answer, but I am curious if others will chime in... Is the barometric altimeter failure a general multisport watch problem, or is it specific to Garmin? It has been a Garmin thing for as long as I can remember (dating back to my Forerunner 910XT). My 735XT never had an altimeter glitch, because it did not have an altimeter.

Many of the Suunto watches do not have barometric altimeters, so that could be a strength by omission. On the other hand, the Coros watches do have them.