Rendered Animation Gets REALLY Blurry

So I have an animation I’m working on, and I rendered a short portion out only to notice that it gets reallly blurry at a certain part where not much movement is happening. Is this a bug with the motion blur setting in the Render editor, or am I doing something wrong. Here is a short clip from the animation so you can see how it suddenly gets super blurry:
(I’m aware of other things other than the blur that need fixing in this clip, but it takes a while to render, so bear with this version)

This is in cycles render and using cameras attached to a soft body mesh for smoother movement.

Also, I’d like to hear opinions on whether motionblur is better applied while rendering like this, or afterwards while piecing together the animation.

are you doing any comp? could be that?

or

This is in cycles render and using cameras attached to a soft body mesh for smoother movement.

Soft body mesh for smoother movement? could make the camera freak out. you should bake out the cameras path after the simulation so that there is no simulations going on at rendertime (select camera -> spacebar -> bake action -> set start / end frames -> frame step 1-> only selected -> clear constaints / parents -> bake data Object -> bake)

Sun beam in the compositor?
Also the camera configuration pointed by doublebishop
Sparazza

comp? as in compositor? I haven’t actually touched anything in the compositor yet.

As for the camera movement:
I rerendered the blurry part of the animation last night, and unchecking motion blur fixed it. I’ll try baking the camera paths like you said and see if that helps.