Form data lost on submit if user takes a long time

Silverstripe Version: 5.4

Question:

I’m having trouble with a trip report form timing out before users have finished entering data. If they take a long time to finish, then hit submit, they lose all their data and have to start over. If they are quick to fill in the form, they’re fine. The form is in the members area of website. How do I diagnose and fix this problem? Any help is much appreciated!