I have the exact same issue. No mods. Every time there's a new update to this game, my manual saves don't load, and I go through the auto saves until I find one that loads. In this update, the first two auto saves didn't load, but the third one did.
from my side, i have disabled auto saves for every renpy game im playing, so im fully dependent upon manual saves only.
in the case of latest update the working save is just before the big fight, which is around 5-10 seconds of the ctrl-skip till the 0.8.6 start.
coding isnt perfect, regardless of renpy updates, coding blocks/stops etc...so i can see if that annoys some players.
yet it isnt that major issue imo here - if you cant load your latest save, try and load some of older ones (those before the last choice, usually works), and ctrl-skip for a few seconds to get to the latest update content.
ofc, those using mods have regular "saves not working", "no new content" etc problems, and those usually dont state they are using mods yet jump right in with their complains.
either way, bottom line should be - save quite often, just in case.
(here and in any other renpy game)