(Resolved) Game consistently crashing in and outside Markarth, making main quest unplayable (With log file!)

[SeizureSalads]

I've been spending the last eight-ish hours today researching what to do to fix the issue causing a crash whenever I attempt to enter Markarth via the carriage or go to an area nearby it, which includes Karthspire and Sky Haven Temple, making the Alduin's Wall main quest impossible to complete without console commands. That's not my only gripe, since I want to 100% a save and that obviously includes quests involving Markarth.
I've tried disabling plugins to narrow the list of possible problematic but it just never really worked. I ended up uninstalling all of them with the exception of Alternate Start, and in an attempt where I did disable Alternate Start, it still crashed.
I've been testing it by quickly making a Nord named Prisoner, using the Statue of Mara to start as a property owner in Whiterun, then run to the carriage to purchase a fare to Markarth, when I then crash immediately after the model on the loading screen appears.
Eventually I managed to get Papyrus logs going and worked with that but it culminated in consistently getting logs like the one attached, with the mysterious MVF1StalkingCellsScript.psc being the last thing to load before it goes kaput.
This VERY helpful guide makes me believe that it's a vanilla issue and I need to reinstall the entire game, especially because I cannot find that script ANYWHERE. The scripts folder doesn't have it, and even doing a scan of my entire C: drive confirming that I cannot find that script.

I use the most up to date version of Vortex mod loader and SKSE and am willing to provide additional files such as mod list, plugin load order, and more at anyone's request.

TL;DR, Todd has defeated me. The Bethesda jank has stolen Markarth and half of The Reach for me and I'm too much of a noob to find the answer.

Papyrus.0.log

[Scythe Bearer]

Before you reinstall the game, have Steam Verify your files.  If you do not know how, right click on the game and select properties.  Then Select local files and then select Verify integrity of game files:

 

[Arthmoor]

The log file you attached makes it pretty clear that when you removed the mods from your game, you didn't start a fresh save to test with. Removing mods from an existing save is going to result in crashes, corruption, or both. The save you are trying to use is toast and you need to start a new game.

[smr1957]

What Arthmoor posted.  The overwhelmingly vast majority of mods CANNOT be removed/disabled mid-playthrough.  For full information as regards this, read the following: You CANNOT Remove Mods Mid-Playthrough

 

As to troubleshooting your build, there is this very general guideline: Troubleshooting Your Load Order

[Arthmoor]

Yep. I would suggest when you start a new game, do so with the bare minimum. USSEP + LAL. Choose the inn start for Markarth, and then walk to where you were trying to get to on the bad save. If that works, you have a stable base and you can then start adding in your other mods a few at a time, reload the prison cell save, and go to Markarth again each time until it starts crashing.

[SeizureSalads]

2 hours ago, Arthmoor said:

The log file you attached makes it pretty clear that when you removed the mods from your game, you didn't start a fresh save to test with. Removing mods from an existing save is going to result in crashes, corruption, or both. The save you are trying to use is toast and you need to start a new game.

Alright, I feel really bad about this, but thanks for pointing it out. I could have SWORN I was starting from a brand new file, I think I just linked the wrong log file, which I apologize for.
I started a new save as a patron in the Silver-Blood Inn in Markarth, and it worked. I'll keep going and keep you all updated.
Thank you again for the help!

Edit: It all worked. The game's files were not compromised and for some reason Skyrim 2020 part 1 was the issue.
Thanks again for all your help!

Edited December 4, 2021 by SeizureSalads
Update