There was a post a while ago about issues with custom code or web service calls within a process. These external calls are handled by the app domain with a default timeout period of 5 minutes. If the call takes longer than this, then the process with throw the following error:
Object '/[GUID]/[Random Characters].rem' has been disconnected or does not exist at the server.
In order for these processes to go through, a longer timeout will need to be set for the external app pool. An official walkthrough of how to do this is available here:
The only issue is that this article is a bit vague on the full steps, so I will give them here:
1. Stop the K2 blackpearl service
2. Edit K2Server.setup and change
<Remoting Enable="False" />
<Remoting Enable="True" />
3. Save the changes to K2Server.setup
4. Edit K2HostServer.exe.config
5. Scroll all the way down, and before </configuration>, add the following lines:
6. Save the changes, and start the K2 blackpearl service again.
I would suggest making a backup of your files before changing them.