It's the last achievement I need. Please does anyone know how to get the "Note from a Dev" achievement?

Just wondering if there are any new tapes or anything coming, or if this game has run its course now?

What I have to do?

The game generally worked well until i came to level 4, which is this hotel like liminal space where you go down this stairway and see a shadow figure thing come out of a mirror or something. So I played the level but couldnt find the exit, so i watched a video on youtube of somebody playing and they just opened the door at the end of this level. Simple enough, but this ♥♥♥♥♥♥♥ door just wont open for me. I have tried like ten times restarting my pc and stuff like that but it just wont work. am sed. (sorr...

https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3320143372