This is a model of 2 components mated with an NPT thread (tapered).

I have applied a fixture geometry condition at the bottom of the housing and a pressure of 2 MPa at the bottom of the cover

I have applied a global contact of no penetration to the assembly.

Standard mesh 

mesh size : 1mm

Aspect ratio : 8

However, This simulation is failing.

I am almost certain that the error is in the connections I have used, and so tried a local contact (no penetration) by choosing the faces of the thread manually. This produced absurd results with the cover deforming radially (not even in the direction of the pressure applied which is upwards) and through the thread of the housing.

What's the solution to this?

Thank you in advance.