In the midst of a fund drive and we're seeing intermittent instances of the message "Your browser session has expired and we are unable to complete your form submission. We have returned you to the initial step so you can complete and resubmit the form. If you experience continued difficulties, please contact us for assistance." on our contribution page.
This is on WordPress, CiviCRM 5.6, using the latest version of the Stripe plugin.
Nothing jumps out at me in the logs -- I do see some weird permission denied on wp-blog-header.php messages but those don't seem to be related in terms of the timestamp, and the site's behaving fine from what I can tell.
Any ideas on what might be causing this and how best to troubleshoot further? Thanks.