Sites that require user login to submit input and that terminate the session after a some period of inactivity.
Web servers that require user authentication usually have a session mechanism in which a session times out after a period of inactivity from the user. This is sometimes done for security reasons, to protect users who are assumed to have left their computer exposed in a state where someone could do something harmful to them such as transfer bank funds or make an unauthorized purchase. Users with disabilities may actually still be working to complete the form as it may take them longer to complete the form than would normally be expected. Upon re-authentication, if the state of users' sessions are not restored, including all data that had been previously entered into the form, they will have to start over. And for these users, it is likely that the session will time out again before they can complete the form. This sets up a situation where a user who needs more time to complete the form can never complete it.
On a site where authentication is required, user input is collected, and which ends the user's session after a known period of inactivity: