Before you upload app to App Store, make sure to do an exhaustive test to search for all of the bugs. Fix them all to increase the likelihood of approval. Remember that building the app is only one part of the process. It will not go live in the store for downloads unless it passes the criteria.
The reviewers are simply there for quality control. They want the apps to be useful to the users. They will reject anything that does not offer useful functionalities or outdated content. They will not accept apps that are copycats of other apps. They will not be happy if the app keeps crashing or showing errors.
Use a reliable app builder to reduce technical issues. Find a website that is known for its reliable tool and support. Set a high standard for the app and adhere to the guidelines.