I have this issue but only when submitting a question from an iOS device. I'm logged in but as soon as I submit my question, I get the following error:

When I tap "Please log in again", I get asked to authenticate using Face ID, after authenticating I end up on the same page, when I press submit I get the above session expired message again. I'm in an endless loop. I've had this issue over different iOS version. I've also tried logging out and logging back in manually again, no luck. I'm simply unable to submit questions to the forum from my iOS device.