Process Activity has ACTIVITY_STATUS 'ERROR' and ACTIVITY_RESULT_CODE ' #STUCK

Hi, We have a custom approval workflow. It has a subprocess (ex: Result 1,2,3) with start, <notification>, END-1 (result: 1), some of the wf processes notification is being sent and getting stuck at the subprocess ACTIVITY_STATUS 'ERROR' and ACTIVITY_RESULT_CODE ' #STUCK instead of branching to the activity flow for result :1

Its happening for few workflow process and not all.

1. In wfstat results it displays

Subprocess  -> Error , Stuck

Start

<notification>

it does not display END-1

2. In WF Monitor it shows the subprocess is complete and result for END-1 as null when it should be 1

3. In WF Test Results (Diagnostics) it shows all activities under '