Late to this, but leaving this for anyone else searching the same problem.
I had the exact same two issues with my dad's old stairlift. Power outage = stuck on the stairs. And the folded chair still blocked half the damn staircase
We ended up with a reconditioned curved one from Halton Stairlifts – UK only though, sorry if you're elsewhere. They walked us through exactly these specs because my dad was paranoid about getting stuck again.