When you are trying to resolve an issue where someone else made an error, put the focus on the error and not the person. Example of this: Instead of saying, “You didn’t send the attachment,” I say, “The attachment didn’t come through, please try sending it again.”
Obviously if they are trying to take your money or being abusive then run don't walk away, but long term friendships go through changes just like any relationship. Life happens.
It's hard to maintain friendship with someone who spends the first 5 minutes of contact scolding me for not calling more.
On the other hand, my best long time friendship is so chill. We can go a year without talking and still just pickup where we left off. The only way to have a lifelong friend is to stay friends.