To replicate:

1. Browse to http://en.m.wikipedia.beta.wmflabs.org/ in a browser window with at least one dimension > 700px
2. Opt-in to MobileFrontend's experimental feature (main menu -> settings -> beta -> 'on' -> save; main menu -> settings -> experimental -> 'on' -> save)
3. Browse to random article
4. Tap/click pencil icon to edit

Current behavior:
Receive error "Error, can't load section"
Expected behavrio:
VisualEditor interface loaded to edit article

When looking through the network requests, you should see an API request for the VE action (something like http://en.m.wikipedia.beta.wmflabs.org/w/api.php?format=json&action=visualeditor&paction=parse&page=0.019064959779951818) with a server response of:
'{"servedby":"deployment-apache02","error":{"code":"parsoidserver-http-bad-status","info":"503"}}'

Version: unspecified
Severity: normal