Problem synopsis: Repeatable instant CTDs when crossing defined "borders" in specific exterior areas. STEP Extended. Edit: SOLUTION: The problem was a misinstallation with the STEP Compilation Patch. Having installed certain--but not all--Extended mods caused the Compilation Patch to not install its full Extended Patch (naturally), and I didn't know to follow the guide for separate patches for those Extended mods I had. Installing all the required missing Extended mods from the guide, and then re-installing the Compilation Patch (now being able to install the Extended Patch) fixed it. I followed the STEP Extended guide (excluding a tiny amount of optional mods) and then carefully installed 15 additional mods myself. However! The main problem persisted even after uninstalling all the additional mods, meaning it might be a problem with the STEP pack itself, which is why I thought it pertinent to post about it here, and see if we might figure it out. (Trying a completely vanilla run with all mods removed fixed the issue.) Problem: At least two large areas (roughly indicated by red circles in the attached image) are unapproachable, as the game will instantly CTD when approaching and crossing some invisible border, or fast travelling to a location within these areas. At first I thought these areas were small, but after enabling all map tags and trying to fast travel to various places, I realized they were larger. (There are most likely more/different places than indicated in the image, as it is hard to pinpoint.) Another thing I just found out: Travelling to some locations, (shown by yellow circles in the attached image--all locations that are bordering on the problematic areas) worked, but upon opening the map screen, the game crashed just like before. Naturally the same happened if I walked too far towards the "danger zone". Viewing any of these areas from afar doesn't pose any problems. Edit: Forgot to mention that starting a new save and fast travelling to (one of the) problematic locations caused CTD as well. Setup/testing: I use Mod Organizer, and liberally use LOOT. I did not apply any INI tweaks aside from those in the STEP guide (apart from the papyrus logging, which was disabled before and after papyrus log testing). Memory Blocks Log tells me mem use are within limits, and papyrus logs gave no repeatable, discernible errors when comparing logs. (The nature of this CTD makes it very viable for controlled testing, luckily.) This is my loadlist (after having uninstalled/removed non-STEP mods): Theories: Now, someone from a thread somewhere mentioned it probably was navmesh issues, which seemed reasonable (though I must admit I'm very inexperienced with navmeshes). Also, someone mentioned the Immersive Citizens mod as a potential troublemaker, although I'd think that--as a part of the STEP project--it was stable (or else a lot of others would have the same or similar problems!). Another theory is that I goofed up somewhere during set-up (probably either missing something whilst reading, or thinking that excluding this or that STEP Extended mod wouldn't pose any problem.. ;_; ) System specs: https://wiki.step-project.com/User:ArchYatin/SystemSpecs