Sorting error
When querying /questions and sort them by creation in descending order, the creation_date drops very rapidly.
I was looking for questions in the [php] tag on Stack Overflow. There are over 1000 php questions asked today, but I received questions that were asked 2 years ago when I get to about 400 items.
This query reveals that they are not really sorted by creation_date at all:
Plotting the creation_date of the first 700 items produces the following graph. You can see there is a weird drop in creation_date all the way to 2008 before going back to normal again.
This problem isn't always present though. I encountered this issue at around 3:45 PM UTC for two days in a row but not during other times of the day.
Filtering error
Another problem with /questions is that if I specify fromdate, todate, min or max when sort by creation, it no longer returns any negatively scored questions.
With this query, I was able to find the typical bad questions in the [php] tag. However, specifying the fromdate has a side-effect of eliminating all the bad questions (click on the image to enlarge):
