When a user is checking a large document back in to Contenta using Arbortext Check in tool , checkin fails with a 502 bad gateway error. 

Keep increasing Application Request Routing (ARR) timeout, (default is 120, 240 is recommended for Contenta) in Microsoft IIS on your Windows Contenta web server until check-in is successful. See https://docs.rws.com/1031737/409590/contenta-5-12/configuring-arr for further direction on configuring ARR

insufficient ARR timeout for large documents