I've had good luck in the past, but I too have had some challenges this year. Almost all of my stays were at two properties, and there's no pattern to what's missing. For comparison.
Starwood - 5 missing 500 PLTs out of 30 stays. I received a reply overnight, but was told it could take 7-10 days to post, and they haven't so far, 3 days later. I was also missing points being redeposited after an awards cancellation. That was a lot more points, and more troubling. It was credited immedidately.
Marriott - 5 missing 500pt PLTs out of 20 full-service Marriott stays. I received a reply 4 hours after sending in the data via their web site, stating that the updates had been made. I wasn't able to get online and confirm until this evening, 48 hours later, and they are there.
Hilton's 8 for 8