TemporalAA - insane blurring when paused

Not sure if the method you use does a full game pause but there is some code you want to look at (maybe remove and it works like you expect it). Search for this:

if(ViewFamily.EngineShowFlags.MotionBlur && GRenderingRealtimeClock.GetGamePaused())
{
	// so we can keep motion blur in paused mode

	// per object motion blur
	Scene->MotionBlurInfoData.RestoreForPausedMotionBlur();
	// per bone motion blur
	GPrevPerBoneMotionBlur.RestoreForPausedMotionBlur();
}

I also suggest to disable motionblur and/or temporalaa to clearly identify which causes the issues. You also can do “show VisualizeMotionBlur” or “vis Velocity”