One of my close friends is being annoying but doesn't realize it, how should i tell them?

So, there’s this friend i have, and they’re really difficult to hang out with. Not that they’re not fun to hang out with, but just that it’s hard to get them there in the first place. What i’m really annoyed at, is how they don’t ever seem excited for anything we plan or even ‘forget’ to show up. Also they won’t let other people know if they can come or not, we literally have to hunt them down just so they can come and hang out.

ex) once, a couple of us planned out a day where we were supposed to do something, we were all excited about it. We ended up waiting the entire day for that one friend to come. We thought maybe something came up, but then why did they not answer their cell or house phone whenever we tried to call? We were waiting for them to pick up, or return our call, or even call us to say that they couldn’t make it… ..... BUT we got nothing. At the end of the day, we decided to phone that person again to see why they never showed up, and they told us that they forgot…. shows how much they cared..

What this one person does a lot is never really let us know if they are able to make it to a certain hang out. We would have to continue asking them, and the answer would always be “maybe” or “we’ll see”, in the end, i or someone else will have to call them last minute to see if they are coming or not (After multiple tries of calling all day might i add).

What should we do? It is difficult to bring up in conversation how annoyed we are of it since everytime i talk to this person, there is no anger and i would be in a mellow forgiving mood, and not want to ruin the conversation.

Sorry if that was confusing to read, I’m not sure how else to reword it. But please give comments!. :p