Unfortunately your problem is a bit complicated and it is difficult to recommend replacing any parts without doing any test.
I had a similar problem last year, customer replaced 3 ECMs and 3 sets of coils (aftermarket) at the dealer and still had the same problem. Since the problem will take 2-3 months to developed, it was very difficult to duplicate once new ECM and coils was installed.
After installing the last set of coils and ECM at my shop, I suggested replacing the engine harness and add a grounding kit (similar to
this one). It's been more than a year and the problem has not return.