just saying, if any friend told me that just seeing an ex, any ex, was like a "oh shit man I better just get outta here this is gonna suck" kind of situation, I would have to assume that there's a social problem with that friend. it is normal to be able to interact like a friend or acquaintance with your ex, it is not normal to be unable to go to a climbing gym if you know that any of your exes might be there.
absolutely, sometimes you end up in a relationship with a real piece of shit and you can't interact with them. but by the time you're avoiding like 3+ different exes, I've gotta assume it's your fault