Good evening.

I have this copy of Fallout 3 GOTY on Steam, but I use the Fallout Mod Manager (got on Fallout Nexus) together with FOSE (got on their main page, fose silverlock org) for patch 1.7. Also with the Unofficial update (last version). BOSS too (but I don't believe it's auto-sorting is the source of problems).

Every DLC is checked, along with other mods I like.

When I finish the main quest line - with sacrificing myself to start the purifier, having Fawkes ans companion - the end cutscene plays, but instead of starting Broken Steel, the credits cuts in and I return to the main menu. I know the contents of the DLC are working because I've seen then during my final gameplay - Sarah and other Paladin fought with Heavy Incinerators, James got hit by an albino scorpion, Fawkes killed a couple of mutant overlords on Vault 87 - but, for some reason, the quest line of Broken Steel doesn't start. When I convince Fawkes to enter the chamber, Sarah hurries inside.

I really don't know how to solve this. Already tried deleting the .ini files, but didn't work out.

You probably have a mod that changes the bodies or the faces. Race mods break the transition to Broken Steel. Use this mod until you get past it:

http://fallout3.nexusmods.com/mods/6240/?

You can remove it once you are past this point.

Although I never installed a mod that does it, some other mod may have did something similar, I don't know. I will try and will come back here later.

I fixed my issue by tweaking the load order. I use Type 3, Project Beauty and Lings on this game

http://www.gamesas.com/topic/1447773-crash-at-end-of-game-before-bos-content-resolved-kind-of/