There is a bug regarding cart and checkout function for 3 page checkout.
Here is a video of the issue,
https://drive.google.com/file/d/13wc4bsoQmAhpWDhJfjzQE8SzSVO7Rh-1/view?usp=sharing
There is a validation function configured on this checkout, which checks the number of characters in the first name. If it exceeds 20, then it blocks the checkout and shows an error.
The issue is, for 3 page checkout, it does not stop customer from going to the shipping page every time, so sometimes customer can go through without any indication of the error, but they won't be able to go to payment page (They won't be able to see error and go to payment button simply won't work). If the customer goes back to shipping then they can see the error and it will correctly block them from going back to the shipping page.
It should block customer from going to shipping page if there is an error. So, customer can resolve it first.
