SAP Workflow gets stuck in intermediate status

Hello Experts,

We implemented a custom workflow that allows multiple users to approve a document.

The workflow type is parallel what means that all approvers are being notified at the same time and could approve the document almost simultaneously.

The Status order is:

1. In work
2. Ready for review
3. Ready for approval
4. Approved
5. In Approval
6. Released

In approval is an intermediate status, user changes the status to approved, workflow engine checks if all approvers have approved the document,

if yes: status is being changed by the WF-BATCH user automatically to released,

if no: status is being changed by the WF-BATHC user automatically to In Approval.

Sometimes, the workflow gets hung in status Approved for hours or days, so whenever the next approver gets in he/she sees the status Approved instead of in approval. By just openning the document the workflow gets hijacked.

Does anybody have any thoughts or suggestions why this could be happenning? And any inputs how we could solve this issue?

Thanks

Ismail