Most of the time payment gateway fails! Money gets stuck for 2-3 days(if credit card), 15-20 days (for debit card) & for any other wallets (congratulations), your money probably is not coming back!
Actually in weekends the number of users is excessively high which they can't handle. They need to the improve the website when it comes to load distribution or payment gateway!
I really wonder why they charge extra apart from movie ticket prices, where service is so poor!