You're not using Xcode. I mean Really Using Xcode. Like making a serious attempt at exercising its features. Hell, you really don't even have to do that. Create a project, edit some code, compile and run your app. That's usually fine. Now, try repeatedly, several times a minute for eight hours straight to use the debugger on your app (intentionally overrelease something or create some other reason for Xcode to launch lldb when your app crashes.)
Xcode will crash.
LOL. For the same reason, Microsoft Powerpoint has never crashed for me in 3+ years. (Because I haven't used it in 3+ years.)
I guarantee you that there is no professional programmer anywhere in the world that has used Xcode to write and compile their applications for 3 years and not had it crash. So your experience would suggest that you aren't one.
Your project is corrupt. You're doing something wrong. Look to a professional for assistance with your IDE.