I have almost 30 of them and they all do it.
Perfectly normal.
If you are worried that it might come unglued, pull the Bolt out and take a look at the bottom of it. When that Firing-pin goes forward, the Lug on the upper edge of the Cocking-piece HOLDS the Bolt in its UNCOCKED (or "Fire") position. As long as that Lug is there, it is 101% safe.
The Lee-Enfield rifle is the SIMPLEST, the FASTEST and the SAFEST design of Bolt Rifle ever put into production anywhere, any time. On top of that, it is easy to clean, easy to maintain, accurate and it will handle almost ANY amount of sheer dirt, filth and abuse.
Remember, the Lee-Enfield is still being used in the North by the Canadian Rangers for exactly ONE reason: they can't find anything else TOUGH ENOUGH and SIMPLE ENOUGH to do the job!
The basic Lee action has been around since 1879 and has been manufactured since 1888 with only a single very small change and a single redesign.
I think you can almost call it a "winner"!