Symptoms

Upload of files bigger than 50MB via K2 process to SharePoint fails with the Timeout error:
"value cannot be null. parameter name: inArray"
 

Diagnoses

The Timeout error is reproducible intermittently by setting the value of the execution timeout to a small number in SharePoint web app web.config file (and in IIS).

Resolution

The following changes should be made in order to resolve the issue:

1. Increase the connection time-out value in IIS settings for the SharePoint web app
2. Increase (or add) the executionTimeOut value in the web.config as follows:

Location: "C:Program FilesCommon FilesMicrosoft SharedWeb server extensions15TEMPLATELAYOUTS"
Changes:
<location path="upload.aspx">
<system.web>
<httpRuntime executionTimeout="999999" maxRequestLength="2097151" />
</system.web>
</location>

Location: "C:InetpubwwwrootwssVirtualDirectories"
Changes: <httpRuntime executionTimeout="999999" maxRequestLength="51200" />

An IISRESET is required after this change.

NB: We have seen this happen with files less than 50MB depending on the configuration per environment