Quest scripts not firing [Dark Brotherhood spoilers]

[esthermoon]

I'm playing the Dark Brotherhood questline (not my first time), and from about the point where Cicero shows up, none of the quest scripts seem to be firing properly. It started off tolerable but got progressively worse, and I'm at the point where I can't continue in the questline because of it. I'll just do a bullet point list (I'll use a different font for easier reading):

 

• I go to the Dawnstar Sanctuary to chase down Cicero, and the door doesn't register that I know the passphrase. I get the default three incorrect options. So I use the COC console command to get into the Sanctuary and carry on the quest as usual. I have to use the setstage command to progress so that Cicero will play his "dying" dialogue. I choose not to kill Cicero and the quest proceeds as normal from there.
• I perform the next few missions without a hitch, up to the first Emperor assassination one. The cook lady doesn't pick up the food pot when she walks me to the Emperor's room, and doesn't open the door -- she gets there, turns around and goes back. I rename and regenerate my Skyrim.ini file, as this has fixed a similar issue I had in the past. Doing this gives her the cooking pot, but she still won't open the door.
• I use the unlock console command to unlock the door and walk in. The Emperor's double is present, but there is no-one else in the room. Naturally the cook lady has walked off, so I use the kill command to kill the double and walk out the door.
• The guard dude (forgot his name) is standing RIGHT AT THE DOOR. He doesn't carry out his whole "I pwn u Dark Brotherhood" speech -- he just has default dialogue ("Hello", etc). His guards don't spawn.
• I use the setstage command again to advance the quest. I travel to the Sanctuary in Falkreath and kill the Penitus guards. I advance the quest using the console.
• I go inside and Astrid is leaning on the door as ever, Penitus agents are having their conversation. I kill the guards and use the console to disable Astrid, as I know she's not supposed to be there. I use the console to advance.
• Arnbjorn is present in both human and werewolf form. Nazir is present, standing in the fire. Everyone is still alive, despite their dead bodies being strewn in the normal places.
• I advance the quest and talk to Nazir, and that fires off normally. The Night Mother then tells me to embrace her, and the quest updates accordingly.
• I enter the Night Mother's coffin, she says "Sleep" and the screen goes black as usual. The screen stays black. Advancing the quest stage does not escape the black screen effect. No matter how long I wait, the script does not fire for Nazir and Babette to be digging the coffin up.

TL;DR: None of the quest scripts are firing for the Dark Brotherhood quest. I'm stuck on a black screen after "embracing" the Night Mother and the quest cannot advance. Loading earlier saves is an option but thus far, has not fixed anything.

 

Has anyone experienced similar issues of scripts not firing? Any ideas? I really want to carry on this questline for this playthrough.