POST requests fail with : IIS 7.5 + ARR 2.0(Reverse Proxy) + OWIN http modules

IIS ARR reverse proxy implementation is failing after my top level application in integrated with OKTA SSO. The OKTA integration uses OWIN modules and WS-Federtaion protocol.The back-end WebSphere app server is logging a socketTimeout exception and the FRT logs on IIS are pasted below.

MODULE_SET_RESPONSE_ERROR_STATUS

ModuleName ApplicationRequestRouting Notification 128 HttpStatus 500 HttpReason Internal Server Error HttpSubStatus 0 ErrorCode 0 ConfigExceptionInfo Notification EXECUTE_REQUEST_HANDLER ErrorCode The operation completed successfully. (0x0) And also two steps up, the General_Read_entity_end shows Bytes received as zero.

-GENERAL_READ_ENTITY_END BytesReceived 0 ErrorCode 2147942438 ErrorCode Reached the end of the file. (0x80070026)

I've put the request.InsertEntityBody(); in both Application_BeginRequest and EndRequest as per IIS7 Application Request Routing (arr reverse proxy) combined with managed module - time out but it didn't help.

IIS 7.5, ARR 2.0, URL Rewrite 2.0, IBM WebSphere 7.0

Any other ideas?

Thanks

The issue is partially fixed by using request.InsertEntityBody() in "Application_AuthenticateRequest" event. Now the Initial page load is successful from the back-end servers. But the events like refresh and button clicks doesn't work. There is no error, the http status is 200 in both fiddler and FRT logs. However the Body column on fiddler shows 0 bytes.