Exporting pages on en.wikipedia may result on a failure, this is being investigated right now. For stability reasons, time to export pages has been temporarily limited to avoid an worse outage, afecting regular page views and edits. While we do not have right now any advice regarding changing behaviours when exporting pages, we advice to check any exports done are successful until this is resolved, specially if done unattended by bots- a portion of those exports could be failing and people may not be aware.

Right now only a single, not-logged-in user is probably affected on en.wikipedia around 1200 times in the last 12 hours, but it could affect in the future other users on other wikis, too.

This is publicly tracked on: https://phabricator.wikimedia.org/T186318

If you use the wikiexport function and it is still working for you/started failing, feel free to provide us feedback on the ticket above. Pregenerated dumps at https://dumps.wikimedia.org/backup-index.html or wikireplicas would be almost universally a better way to get mass-revisions.