With all due respect, your experience does not match mine, and I suspect that of most members, otherwise we'd have a long thread about these issues. In my ~10 years as a member, knock on wood, I've never had a stay not post at all, the incorrect number of tier nights posted, or a promo/bonus not or incorrectly honored. The only issue I've had, on ~5-10% of my stays, is an incorrect eligible spend leading to incorrect base points awarded. I'm not dismissing your experience; I'm merely pointing out that you are very likely in the minority, and I'm sorry that you've had a string of frustrating experiences.

As for how to better handle these issues, I think you're doing the best you can. You could try Twitter DM, which allows you to clearly spell out your issues and communicate asynchronously, i.e., the agent on the other end can do their own research without holding you on the line, but it could take time to put all the details in writing. This could also be done via email if there's a generic customer service/affairs email address.