my garmin 510’s gradient and elevation was way off on this mornings ride
saying i was decending when i was climbing and all over the shop.and elevation on readout was almost level.
would low cloud or a dirty screen cause this.

Did you recalibrate it? Sometimes that’s all it needs.

I usually start mine on top of my wheelie bin whilst I get the bike out of the shed. Pick it up and discard the ride.
It’s almost like letting it calibrate itself before I start it for proper.

thanks for the replies
first time it’s happened in 6 months.
will try the above before the next ride.