Sounds like (or similar to) a classic Mavic freehub seal issue. Well known, well reported on several forums, for Crossrides and the Road hubs too.
Those pics look different to my old Crossrides, though.
On mine, it’s an allen key to remove the axle and freehub, and the classic yellow PTFE friction seal in there is the culprit.
It’s not just backpedalling that’s the issue, but also freewheeling… eventually you hear a “squeeking” noise, and the chain goes slack, because the cassette tries to keep turning. I’ve had to pedal permanently to get home.
Plenty of youtube vids etc. before when I looked. Aksium etc. road hubs were identical to crossrides.
I have a bent axle on mine though too, which makes it uneconomical to fix.