Has there been any issue recently at the port of entry for a B2 visitor visa?

My parents are coming here in May. They already have their visa and they have the tickets booked as well, including the return tickets. I was just worried if there’s been an issue at the port of entry recently and what kind of questions are being asked. As of me, I am on the H1B visa directly with an end client.

All visitors from Middle East and India must expect and be prepared for secondary screening where an officer will interview to determine purpose of visit and consistency of information with the CBP form that they filled up during last few hours of their flight. However this is nothing new and has been happening randomly for past 16 years. It is just more frequent now in 2017