Bell refers to it as Vortex Ring State - similar to other helos - but this particular problem is unique/compounded to/in the Osprey due to their asymmetric blades when encountering their own downwash at higher sink rates & low forward speeds. The parameters aren't vastly different from most other helos.
Any new aircraft will have problems - designing a new type of aircraft and employing it as a military weapons system with such a radical departure from traditional/conventional configurations is bound to have even more problems.
For the record, 4 crashes (plus a prototype crash) - 26 USMC & 4 contractors KIA.