Board Thread:Support Requests - Getting Technical/@comment-26456975-20150606042740/@comment--20150606045317

It is a known issue. Could you please do a report to Staff about this? They are currently working on it, and the more reports, the better they can track the source down.

"We're currently looking into an account session issue that may cause edits or uploads to fail (with an error message like 'your session expired'). If you're being affected by this, please let us know any details via Special:Contact. Thanks!"

- Kirkburn, Technical Update: June 1, 2015