Xcode 15.1, iOS 17.2 – no updates. The "Connect via network" is still unable to uncheck.

Sorry, I can't, there are a lot of network requests and I didn't know which one exactly could cause the trouble. But it appeared only after upgrading to xcode13. I've solved this by replacing an options parameter in all NSJSONSerialization method calls to kNilOptions: [NSJSONSerialization  dataWithJSONObject:dictionary options:kNilOptions error:&err];