am i in the wrong for being irritated?

So i have a 9mo son and a 19mo step son, the step son has 50/50 custody between mine and bfs home and the moms home. we do custody swap backs saturday nights at work, she comes to us and drops him off and then we take him back once our share is over. with lent being a crucial busy season for restaurant we both work at the hours got pushed back till 9pm on saturdays so that kind of messed up or custody swap. when we first found out about the change my bf and he talked about her dropping him off at my mothers house. ( for context he is post liver transplant, my whole family has been in his life since he was born, we were all down at the hospital every weekend so no we are not strangers. me and my bf have also been together since his first son has been born so it’s not like i am intruding either.) she agreed to dropping him off at my moms which would be an hour max, just do we have time to get out of work and we already grab my son from her anyway. it was also convenient because she lives 2 minutes from work. 2 days before this new swap is supposed to happen she decides she’s not comfortable..she agreed to this 5 WEEKS AGO, but she does this out of spite with everything constantly. i’m irritated because this makes my life harder once again because she can’t be an adult, she thinks everything is her way or no way. i now have to go pick up my son, go back pick him up, then we all have to unload the car and bf has to go back to work to get the rest of his stuff. there’s no point to this post other than im pissed lol but if anyone wants to add how we can approach it lmk, it’s a 50/50 split with mutually agreed swap location. and in this situation work is not mutually agreed on so idrk how to go about it.