Elevation is no longer accurate (1 year after purchase)

I purchased my 5 plus over a year and a half ago and everything was working fine. I run and bike through suburban areas in the bay area. The elevation gain typically matched strava's map. However, over the past year, the elevation charts are horribly wrong. For a 5mi run with 85ft climb according to strava, it would say 890 ft accent and 800 ft decent, and the reported number on connect/strava is the insane 890 ft. This is impossible to do in a flat suburban area, and was not the case a year ago. I factory reset the watch and attempted to brush the sensor, but nothing has changed. What more can I do to address the inaccuracy of the elevation?