When you have an IPC process, this takes about three hours to complete. It appears that the child process executes just fine, but it takes while to continue with the parent process straight after.
When you go into the viewflow of the process and click on the activity to view the process time, this will display as three plus hours or just below.
Check to see if the SQL Server time zone is different to that of the K2 server. If this is the case, update it via the control panel by navigating to date/time settings. After this the IPC process should be able to execute much quicker.