TypeLoadException… reason?

[d00_ape]

I’m trying to make a cast between two classes like this

AcadEntity entity;
…
Autodesk.AEC.Interop.ArchBase.AecWall wall = (AecWall)entity;
First time I run this an TypeLoadException is thrown. The second time I run these lines it works and the wall instance works perfect. How come it fails the first time?

The Exception message looks like this:
Could not load type Autodesk.AutoCAD.Interop.Common.IAcadObjectEvents from
assembly Autodesk.AEC.Interop.ArchBase, Version=4.5.202.0, Culture=neutral,
PublicKeyToken=d672471c03b2c408