It’s a survey, there are a lot of non-responses (getting worse) and late responses. They try to correct for this, and that normally works, but when “weird” things are going on the corrections can be pretty wrong. The people who use these numbers understand all of this and it’s fine. It’s just the popular media that freaks out.

The quarterly numbers come from better data sources (tax withholding, unemployment insurance payments, etc)

For example, if a small business goes out of business and fires everyone, they probably won’t respond to the survey. If the rate of small business failures is not what we normally see (more of less is absolute of relative numbers) it can create a bias that throws the models off.

Let me guess, they are calling landlines. And no one picks up unknown numbers on cell phones. They are hopelessly behind the times