Shut-In Royalty Payments

Hello, we’ve been receiving shut in royalty payments on a lease we inherited from our Mother when she passed away in 2017. The well name is Leggett Gas Unit #1 (LGU#1) in Shelby County, Texas - API #42-419-31053. We have records that show there were royalty payments paid to her up until 2012 and then, in 3Q12 it was switched to Shut In royalties. It was my understanding that a Shut In well was a temporary situation. We don’t have a good understanding of Shut In status and would appreciate any information. Thank you