This is afaik typical for MCU films. Often they are "discovered" in the editing bay. Which is why Disney /Marvel bring in uncredited talents and do reshoots to help assemble their films in post. It's why there are sometimes late drastic changes. One example being Odin's death scene in Thor Ragnarok. They changed the setting, tone, and dialogue of that scene by doing reshoots.
This stigma of reshoots really needs to end. In this day and age when films are so often assembled in post rather than the script stage reshoots have become so common that they are the norm for blockbusters and not a guarantee of bad things. Or even a guarantee of good things. They just are. A normal typical part of the Hollywood filmmaking process.
And the Russos havent failed us once. Theyve delivered 3 really good top quality films. Especially after Infinity War, I'm willing to trust that they and Marvel have things under control.