It's normal, don't worry about it. Actually if it closes by itself the carrier latch may be a little weak, but nothing to worry about.
I beg to differ, it's not normal -- that's not the way 11-87s are supposed to function! Although many auto-loaders are similar in appearances, they don't all load the same way.
aTm papi's loading procedures aren't those recommended by Remington for the 11-87. If you don't have an Owner's Manual, download one from Remington by clicking
here.
Like the 1100, the way the 11-87 is constructed, the condition where the bolt is locked back normally occurs only when the magazine tube is empty. Think about how the 11-87 normally operates: when it's fired the bolt opens and the freshly fired hull is ejected. The bolt then has two options: If the magazine tube is empty, then it locks in the rear position (ready to be loaded). Or, if there is a shell in the magazine, it doesn't lock, and returns forward loading the next round.
The recommended loading procedure is to load the first shell through the ejection port opening with the bolt locked back. With your fingers clear of the opening, push upward on the carrier release and the action will snap closed. The first round is now loaded, for additional rounds, load from the bottom and into the mag tube. (The official Remington version includes using the safety button.)
The way you load two from the bottom, then you have to manually retard and release the bolt to move the first shell from the mag to the chamber. Doing this by hand is dynamically different than when the gun does it automatically -- you are essentially "soft shucking" an auto-loader (and look like a total newby in the process). Watch any experienced Remington shooter load a 1100 or 11-87, it's always one in the port then hit the release.