I'm starting to play the Phantom Liberty DLC, and right after the president's plane crashes in Dogtown, the game glitches. As soon as I get off the slide, Songbird calls me and says I failed the mission, and sends me outside of Dogtown, with Johnny waiting. But the "Hole in the Sky" mission doesn't disappear, even though I'm outside and Songbird says the president died. The mission continues, asking me to enter Dogtown and go to the crash site, but even going there, nothing happens; the mission doesn't progress. Help me, I've already tried everything suggested in forums.
Ok
I assume you already tried to load a save created before the "Space Force One crash" cinematic, just in case?
Unfortunately, mods can cause unexpected issues and it's just a guess, but I think this is exactly what happens here. You can try to disable (or remove) your mods, but there is a good chance the issue will still occure, because mods data will remain in your save files anyway (removing/disabling mods could create even more issues).
You can also check on all pages of the mods you're using if someone else encountered a similar issue and find a way to fix it.