error page showing entire ERR_READ_TIMEOUT message

Reported at https://en.wikipedia.org/wiki/Wikipedia:Village_pump_%28technical%29#Wikimedia_Error_editing_fairly_large_article

Reproduced in IE8 and FF

This actually seems to have two failure modes:

1. I copied the entire contents of the Hyderabad page to my Sandbox. After clicking Save, the browser doing the save never returned, just spun forever, even though the copy of the Hyderabad page was saved correctly to my Sandbox.

2. In the Sandbox copy, I edited the section on "Pollution control" once in FF and again in IE8, and upon clicking Save both times, got the ERR_READ_TIMEOUT error page as reported in VPT, screen shot attached.

This is probably not relevant, but the page displayed a banner reading "This article or section is currently undergoing a major edit by the Guild of Copy Editors. As a courtesy, please do not edit this page while this message is displayed." at the time of editing.

Version: 1.21.x
Severity: normal

Attached: