Hi, I think I have fixed the problem. In the time since I posted, I completed The Pitt with no further problems and went on to Anchorage, where this I encountered a game breaking bug shown here: https://imgur.com/a/8rAcVZs. Just like before, disabling mods didn't change anything so, noticing how these bugs had only appeared on some DLCs so far (I didn't encounter any issues on Mothership Zeta), and remembering that I had cleaned them at the start, I resorted to bringing back the original ESMs from a backup, without deleted navmeshes or FO3 QAC. This fixed the issue on Anchorage, and, I imagine, The Pitt too. Turns out that using FO3 QAC on Anchorage.esm causes the issue. I don't think it's my fault because I have followed this tutorial: https://www.youtube.com/watch?v=69hyaD9Efvw to the letter and I am capable of reproducing the issue every time I QAC that ESM. On the load order topic, I have ended up with this one: 0 0 Fallout3.esm 1 1 Anchorage.esm 2 2 ThePitt.esm 3 3 StreetLights.esm 4 4 BrokenSteel.esm 5 5 PointLookout.esm 6 6 Zeta.esm 7 7 Unofficial Fallout 3 Patch.esm 8 8 Project Beauty.esm 9 9 DCInteriors_ComboEdition.esm 10 a aHUD.esm 11 b iHUD.esm 12 c RH_IRONSIGHTS.esm 13 d Project Beauty- Broken Steel.esp 14 e Project Beauty- Point Lookout.esp 15 f CASM.esp 16 10 Fellout-Full.esp 17 11 Fellout-pipboylight.esp 18 12 Fellout-Anchorage.esp 19 13 Fellout-BrokenSteel.esp 20 14 Fellout-PointLookout.esp 21 15 Fellout-Zeta.esp 22 16 GNR Enhanced.esp 23 17 dD - Enhanced Blood Main.esp 24 18 Flora Overhaul.esp 25 19 Sprint Mod.esp 26 1a Realistic Interior Lighting - OA.esp 27 1b BetterGamePerformance.esp 28 1c Realistic Interior Lighting.esp 29 1d Realistic Interior Lighting - BS.esp 30 1e Realistic Interior Lighting - PL.esp 31 1f Max Level 99.esp 32 20 RH_IronSights_Basic_VanillaPlugin.esp 33 21 RH_IronSights_Basic_AnchoragePlugin.esp 34 22 RH_IronSights_Basic_PittPlugin.esp 35 23 RH_IronSights_Basic_BrokenSteelPlugin.esp 36 24 RH_IronSights_Basic_PointLookoutPlugin.esp 37 25 RH_IronSights_Basic_ZetaPlugin.esp 38 26 RH_IronSights_Pitt_NewRifleSights.esp 39 27 RH_IronSights_RemoveReticule.esp 40 28 RH_IronSights_PL_NewItems.esp I don't mind if it isn't perfect because I'm 80 hours into the game and everything has worked out well.