We ran nylon wheel bearing parts that required press fit assembly in different configurations including what you are describing. We never found a successful process that would produce consistent parts after final assembly. Then we added an annealing after molding. The annealing process relieved molded in stresses, open the process window and solved the problems with failures after assembly. That maybe the step the previous molder was doing and it didn't get pass onto the new molder. Dupont plastics has really good information for annealing nylon materials in their design guides.