For an application that is essentially just a bunch of open mel scripts, Extensibility is a BUILT IN Maya function. And was at one time celebrated for it.
What are your computer specs? Sometimes unreal will downsize textures when memory is scarce, sometimes quite a lot. Not usually to that extent, but I imagine it could happen with a lower spec computer, or with a graphics card that isn't quite compatible. UE eats up a LOT of RAM too.