Terraine affecting volumetric lightmaps been built properly below the terraine

PhantomFox

Hi Guys! 
Im creating level interior with another section above that interior which uses a terrain. 
I'm coming across an issue where the terrain is stopping the volumetric lightmaps been built correctly compared to the section above the terrain. 
Is there a solution for this one of you might know of? 

PhantomFox

Think I found a solution by disabling static shadow on the terraine, but still curious if anyone has alternate solutions to this I could also try