Although it is not typical, it occurs on mt-2 vials...I wouldn't be alarmed, the product should eventually mix/reconstitute. Please keep us posted, hopefully you will not need to wait overnight.
As I said in another thread it could be where the powder has created a protective barrier.
Using the same analogy, think of custard/hot chocolate/milkshake powder, if it's not whisked properly there are lumps, inside these lumps are dry powder, even though the outside is wet.
It has probably done that but on the side of the vial.
I just tried MTII for the first time (after using MTI). This never happened with my MTI and I bought it from the same supplier. I tried 3 vials because I got nervous and it happened with all 3. Does anyone know why this happens with MTII and not I? Or is it just a fluke. (granted, I did have the MTII in the freezer for a while).