Ryanair allows you to change booking for a fee, as long as its not less than 5hrs before the flight. Bug is that this feature is basically broken and I couldn't

Ryanair allows you to change booking for a fee, as long as its not less than 5hrs before the flight. Bug is that this feature is basically broken and I couldn't change the booking even more than 12hrs before the flight. The button for selecting a different flight does not work (you can search for different flights but cannot select one). Because of this I was forced to book a different flight separately, which was more expensive than simply changing the existing flight.