Release strategy reset automatically while doing mass change in po

When we try to make a mass change using t code MEMASSPO

We are trying to close old purchase order by checking field Deliv. Compl ( MASSEKPO-ELIKZ ) and entering a old date in field Latest GR Date (MASSEKPO-LEWED).

First scenario

If I create a purchase order then I used t code me29n in order to release it. But before I released it I decided to delete a line then release it. The next step went and made Mass change on those 2 fields mention above the release strategy gets reset.

Second scenario

But if I created a purchase order then I used t code me29n and released it and saved. After that I press change and delete a line. The next step mass change and I changed the same 2 fields mentioned above the release strategy stay the same and doesn't get change.

Thank you in advance.