When the mist disappears, alduin doesn't fly towards me and the 3 other heros, instead he flys down on the left road and just stays there. We have to go hunt him down ourselves, he still attacks but he never flys and he also cannot be harmed in anyway possible. Anyone else has this problem?

The only mod i have that changes the stats of alduin is Improved final battle, but i read the comments on that mod and nobody else has this problem. And none of my other mods alter alduin or sovngarde in anyway. Anyone know how to fix this? thanks in advance.

You should probably uninstall that mod and try it out. I'm willing to bet that it's the source of your problem. You're having troubles with the final battle, and you have a mod that alters the final battle. Put two and two together.