I don't have any of the issues you describe - I'm using a Mac and iPhone. One thing though - the FIRST thing I do is log in to my account, then I go shopping for flights, choose seats and confirm my payment. It takes me very little time to complete a booking because mine and my partner's Elevate information is in my profile, as are two credit cards I used for method of payment - so no issues with timeouts, etc.
YMMV