I have a document in document library and it has 1.0, 2.0 major version and 2.1, 2.2, 2.3, 2.4 minor version. When I click "Delete Minor Versions" or "Delete All Versions", the last major and minor versions are not deleted. I know last major version is required but why last minor version is not deleting? I have searched why this is happening but couldn't found any help on it. Can you please provide me some reason or explanation for this behavior of document library?
Pretty sure that if the newest version is a minor version, that will not be deleted when using that. You could try creating a new major version (it would be the newest version, then "delete minor versions", which should remove all minor versions).
I just tested the above scenario and this worked for me.