Rendering Issues with Overlapping Smoke Domains

I have two smoke domains using separate flow fields, which overlap with one another. In the area where they overlap, as in the attached scene, there are some obvious rendering issues:
SmokeDomainOverlap.blend (479 KB)

What’s going wrong, and how do I fix it? Thanks!

Have a look here : https://blender.stackexchange.com/questions/77547/smoke-domains-overlapping
But why render with Internal ?