On a recent ride with the 840 i have encountered a bug with strava segments, i wasnt following a route at the time. When the strava segment came up it said i had 42950km left on the climb and then froze on this "page" without brining up the strava page... I slowed down and took a screenshot.
I notice you cant upload the FIT file directly to the forums? I have uploaded the FIT file here www.dropbox.com/.../2023-05-27-08-23-02.fit for the ride if this helps.