As a rule of thumb, EXOS defects found are fixed at a given time. They are applied to all supported EXOS versions at that time. It is possible that a given release will need more effort to have the fix included. New patch version of a supported EXOS are released at a given pace, and not necessarily all at the same time. That means that a given EXOS train might have the fix included before another release.
So it's more about time of release of the patch, rather than a version number, if you're following me.
That being said, 16.1.3 is a rather recent version so either it's a new issue, or there's something to look at more closely.
Release Notes have the list of bug fix. Before an upgrade I'd recommend checking that the fix that you need are included in the new release.