I've bought Edge 840 recently and it was on some old version. So i've tried to build a path there with minimize ascent / minimize distance options there – was ok.
Then i've updated to last version 25.25 and minimize ascent clearly not working here (honestly i think minimize distance too – they behave like inverted to each other).
For me it looks like on the latest version minimize ascent tries to minimize distance and minimize distance minimizes ascent