We are a plastic injection mold and molding factory in China. As our experience, there is no soft material could overmolded with POM for the POM performance . Our suggestion is that take a new plastic material for hard part instead POM, such as PP, ABS. What's more, for the hight melting temperature for PC, cannot be overmolding material either.
I have seeked our Chinese technical support team, they advice you to use ABS, ACS, PP instead of the POM, I have also check the fitting list, it shows that there`s no available material for goog adhering.

We had found a partner resin to over mold with, but other than that, I haven't seen an over mold resin for POM. I suggest that you change the base resin, then you can get good parts. I expect several injection mold changes to be required to get the dimensions back in spec from our Chinese injection mold factory. I am from China and I remember the time that just Aco Mold places more then 800 injection mold each year in China. We all learn a lot about how to deal with Chinese companies and we have some of the best injection mold tooling companies in China. We have a strong commitment with the customer and we are aware of your main concerns. By other side over here nobody charges for regular plastic injection mold sampling, they only do for pre-series productions. The time difference is nothing compared with China and that make it easier to communicate.