This happens all the time to me in a variety of situations. One is when you get a person who goes into the subway and immediately stops because they see that there are no seats available so they decide that they’re going to take one of the two coveted door standing areas even though they know that people are still trying to get in. Or it could be that you’re just trying to get out and it’s crowded so they don’t want to lose their standing space by making room for the people who need to get out.

You say “excuse me” and both backs are turned and sometimes they’ll shuffle in place a bit in place without actually making any room for you to get by because they’re both gambling the other person is going to be the one to move. Should this happen you’re forced to touch both of them more than you intended to as you squeeze between them or maybe rudely push through them because you’re frustrated and you want to make your point. My approach is always the former because I’m not looking to actually shove people around despite how much I might enjoy it.