For the past day or so, we've been seeing an intermittent and annoying problem with Amazon.
When updating the ranks for all the books being tracked by Booklert, the Amazon service to find out the rank is sometimes reporting an error - meaning that each hour a few of the books don't have their rank updated.
It isn't always the same books, and sometimes more fail than at other times. So far we haven't been able to work out a solution to the problem.
The ranks reported for any book will still be correct, but at times they could be a little out of date.
After investigating to ensure it isn't anything that Booklert is doing wrong, we've raised the issue with Amazon. They've told us that they're aware of the issue and are looking for a fix, but it might be a few days before it's working flawlessly again.
Update: I've left it a while to ensure that it wasn't a temporary improvement, but Amazon seem to have sorted things out.