Forerunner 965 software version 21.20
This bug were introduced in recent software version update. Earlier software version had no such problems.
In activity "Climb indoor", if a route is down-climbed (with pressing "Back" button for start a new route, setting difficulty and pressing "Start", then down climbing, pressing "Back" button again for stop the route), then all the ascent and descend values of all the earlier recorded routes in this activity are reset to zeros.
Also, during the "Climb indoor" activity, watching the elevation chart showing elevation changes in real time as I climb. However, any route being down-climbed makes the elevation chart being reset to a flat horizontal line (no elevation gain nor loss).