Despite the general unhelpfulness of the email customer service (both IME and as reported here in other threads), I sent them an email about a recent stay which didn't credit properly and they credited the right amount of points within a few hours.

I also emailed the hotel a few days before emailing Hilton directly - the hotel replied after Hilton did, so it's possible that the hotel actually took a few days to fix it, and it was coincidental that I emailed Hilton at the same time