Ant-Man is like the underdog of the Marvel Cinematic Universe at this point. It doesn't get the big attention, but it definitely delivered from its first solo outing. Now with its sequel; Ant-Man and the Wasp, coming out this summer, maybe it will bring more hype around this time.
Regardless, it seems to be apparent that there have been some reshoots for this upcoming Marvel film. BadTaste.It reports that it is currently going through some reshoots in Los Angeles.
Reports also say that it's because they wanted to change the whole opening action sequence of the film. Nothing has been confirmed as of now, but there's plenty of time before it's release date. Whatever changes need to be made, will surely be the right ones.