Ok, after pooling more knowledge from our team I believe this solution will work for you. The engine calculates on a space from 0-1. Sometimes, when you build outside of this space, you have to tell the engine to calculate the full amount of UV space that you have assigned to an object.
What you will need to do is double click on the floor inside of UE4. This brings up the detail panel. From there, on the right side, click the “Build Settings” roll out tab. Under that tab is an option to “Use Full Precision UV’s.” Check this box on and hit apply changes at the bottom of this section. This tells the engine use the full UV space provided on this mesh.
I just tested this and it eliminates the UV issue.