Submitting an old version of a Form can result in various issues from Connector errors to duplicate Auto-Numbers on the back end. To avoid these potential problems, consider checking the "Wait for Sync on Load" checkbox within the Advanced Options section of Apps > App Setup (highlighted below):
By default, the app will perform all data syncing in the background, allowing the user to immediately start working while the sync is still in progress. When this option is enabled, however, the app will instead display a blocking overlay when syncing, forcing the user to wait for the sync to finish. This will only occur when the user logs into the app or resumes the app from the background; other background sync intervals will continue as normal. This is useful for cases where you must ensure the users have the latest data before they start working with the app.