Gradient chevrons

I notice there are now OS style gradient chevrons on the map. They point the same direction as OS chevrons, ie downhill, but appear in places where there are no chevrons on the equivalent OS mapping, so they're obviously using different data. So my question is what are the gradient and/or altitude gained and/or distance of road definitions for these chevrons?

Thanks!

Android app no longer working

More precisely, it's working at a bare minimum: calculating routes, displaying them and – usually – tracking my whereabouts. But at that level it's simply like my old Etrex with a better screen. What it's not doing is: 

• Giving voice instructions
• Giving on screen turn instructions
• Dimming between turns
• Re-orienting the screen at turns, or indeed orienting it when starting. 
• Sounding the off-route klaxon

This happens regardless of whether I use the "Where to?" or the "Plan" button. Activating "always access location" makes no difference, and I can't work out what the "Follow" button is doing, if anything, but the useful functions do seem to have disappeared at about the same time those two changes were introduced; maybe that's just coincidence and I wouldn't swear it was exactly the same time.

This is on a Motorola Moto E7 running Android 10.