Thanks for the tip. I actually tried a couple of things, cleaning included. Eventually it was my SanDisk 64GB microSDXC card that was running funny. I moved it from my rezound n never reformatted it to the m8. I popped in a Samsung 64GB microSDXC, brand new, n it worked like a charm.
The odd thing is I don't understand y it just kept saying microsd unexpectedly unmounted. Maybe it it just needs to be reformatted or maybe my sdcard is dying. Gonna reformat the SanDisk and try it again on phone later. If not gonna send it back for warranty