Issues where features that work correctly in Playtest do not function after publishing the island live in Fortnite.

We are experiencing a problem where several features of our UEFN project work perfectly in Playtest, but after publishing the island and testing it live in Fortnite, these features do not work anymore, or only partially. We have not changed anything between the Playtest and the live version.

The specific features affected are:

Killstreak counter not registering at all
Event sounds (e.g. on kills) not playing
Custom animation with a piggy bank (supposed to fill with money and then drop weapons) not triggering
This makes it very difficult to test and release updates, since the Playtest gives us a green light but the live environment behaves differently.

We would like to understand why these discrepancies occur between Playtest and published versions, and how we can ensure that what works in Playtest will also work correctly once the map is published.

Help is much appreciated and thanks in advance!
This is the second question again btw, this is the account that is effected by the problem.