PPF Processing Issue from Wave Release

Hi EWM Guru's

After releasing Wave and confirming Pick Tasks, Pack list PPF gets triggered.

Now let us assume a wave has 300 or more ODO's, there is always one or 2 ODO's which will be unprocessed or processed late.

I mean to say PPF Action will not get triggered and hence Pack list spool will not get generated

I checked PPF Schedule and Execution conditions and do not see any issue.

Any Idea, why only 2-3 ODO's has issue while all get processed fine?

BTW, this happenes only in 2 step picking.

Thanks!

Kamlesh