Flag Physics seems fine when on the viewport but looks messed up when rendered I'm fairly new to blender and I've come across this issue. My flag with wind physics seems fine when I animate it on my view port using collision physics. 

Here's a sample:

https://imgur.com/qmJvESK

But the moment I render the animation the flag seems to spins around then the meshes seems to break.



https://imgur.com/W4as88R
Do you have any subdiv modifiers for that flag? If so make sure they have the same amount of subdiv steps on render and viewport. Because the gif you posted seems to have more geometry on it than the last image you posted...