Unable to update mesh with new uv channels

Does anyone know what might cause UE4.10 to not update a mesh when overwritten? For example, I imported an fbx object which had bad lightmap uvs in channel 2. I checked the uvs in UE4 and they were overlapping. I went back to maya, fixed the uvs, saved and over wrote the same file in the UE4 content directory. UE4 reported a change. I then checked the model again in Ue4 but the uvs never updated. I tried reimporting the model, but the uvs still did not update. I double checked in maya and they were fine. I then exported another version of the same model from maya into the same folder in the contents directory structure. When I viewed these uvs in UE4, they are now clean. Strange.

Does UE4 cache some of this data? I even restarted UE4 but still get the same issue with the original file. I have my workaround but just want to know why this might be occurring? Any ideas?

I found if I delete the associated .uasset file and re-import the mesh, then it updates properly.

I’m having this bug myself, it’s the most annoying thing. I wish these basic things worked correctly in UE4.
Indeed, the only way to fix this, is to delete the .usasset and reimport all over.