When vials are tossed at moving players greater than a few paces away, they change from a forward toss to a massive parabolic arc that usually puts them into ceilings.
It seems to be working correctly for me. No armor feat on warforged and 2nd core = magic missile immunity. Adamantine body feat = no magic missile immunity. Light armor on shadar-kai = magic missile immunity. Medium armor = no magic missile immunity.
What gear do you have? What race? This may be an isolated bug happening with certain races/gear/etc.
Not a bug. Part of vial throwing mechanics. The trajectory of the vials thrown can be manipulated.