There is more than one, they are not the same object, and the difference is the whole argument of two of these stories.
Most people watching these films think there is a shield. There are at least three, and the catalogue lists them separately because the story keeps turning on which one somebody is holding.
The first is made by Howard Stark from vibranium and given to Steve Rogers during the war, and it is destroyed in the last battle of the Infinity Saga. The one Rogers hands to Sam Wilson afterwards is an alternate version, which is a small phrase in a reference work and a large hole in an afternoon. And the third is scrap metal, welded together by a man who was told he could not have the second.
Show detailsWhy the second one exists
The shield Thanos breaks in Endgame is the original. The shield Rogers gives away at the end of the same film is described in reference works as an alternate version, because the man giving it away has just come back from living a life in another timeline.
The films do not explain this. It is one of the clearest cases in the whole catalogue of a continuity question that has an answer, but only if you go and look for it.