I have the same problem described in this article from 2009 https://help.k2.com/kb000541 (Hotfix: IPC Event processes are completing but the activities in the calling process are not).

The error resolution was:

This Hotfix is contained within the latest K2 blackpoint 0902 Update. Install the update package to resolve the error.

This was a very old fix (from 2009), but I am experiencing the same issue now.

Workflow1 has an IPC call to Workflow2. It is a "Synchronous (wait for the child process to complete)" call.

Workflow2 has an IPC call to Workflow3. It is a "Synchronous (wait for the child process to complete)" call.

Workflow3 has an IPC call to Workflow4. It is a "Synchronous (wait for the child process to complete)" call.

During execution, Workflow4 and Workflow3 were completed successfully without any errors (the status of both workflows are Completed), but in Workflow2, it shows that Workflow3 is still Active.

How can I fix this issue ?

Thank you.