i dont think you need any additional contact except shrink fit contact for your analysis. but i can suggest have u used softspring option or inertia relief to stabilise ur model.
or have u used any constarint to fix the mivement of assembly?
also some times solver fails due to higher number of nodes which limits your computers resource. so try to use symmetry condition. and also use direct sparse solver to solve these kind of issue.
Also want to know what kind of study u are running? is it non-linear or just a static study?
Devi Prasad Samal