I don't know how else to remedy this or fix it, but for the past three days, I've noticed that whenever I'm near O'neil Ranch, it is engulfed in flames. FD can't even put it out. There's also this random plane in the field near the highway. I feel like some story stuff leaked over. None of this is present in single-player. Does anyone know a fix?

While I cannot explain to you why that is in your game, I can tell you where it comes from.

• The plane is from the mission "Caida Libre", which has you shoot down the aircraft from the observatory with a sniper rifle. You then follow the plane into Blaine County, where it crashes.

 

• The burning farmhouse is from the mission "Crystal Maze" in which Trevor enters the O'Neil ranch, kills a few of the family members and then sets the mansion on fire. 

I went there in my 100% savegame, and the plane isn't there, nor is the house on fire. It burnt down.
I'm guessing that is due to some mods you have installed in your game.

@Lennyy Thank you. I'm wondering if Enable Interiors has anything to do with it. I know mine needs an update. I'll give that a try, then maybe kill this off.

That sounds plausible. If you fix it, perhaps give us an update in case anybody has a similar issue in the future.

OK. Not surprisingly, I ended up removing Enable All Interiors, and the above issues have been remedied.