Make the exact same behavior in a version of the Android API does not look too professional?

I have problems implementing some behavior in an application that I create, exactly when this application is run with Android API 28 (the last one by the time). Be able to implement it correctly in all previous versions supported by my application. It seems like it's a pretty hard thing to implement in this version because I've been researching for hours without advance.

The point is that I could almost maintain all the behavior mentioned in this API with a simple change. This change would make the user experience slightly worse, but nothing too troublesome.

If I decide to do it, then I wonder what might be the best of the two open possibilities:

1) Keep the entire behavior in all previous APIs, but change it in the API 28 (and later). Thus, although users with API 28 (and probably the following) get a slightly worse user experience in this, the rest can get the improved version).

2) Make sure that all previous versions retain the same behavior with which I would modify the API 28, as this might look too unprofessional in this API (and probably later, if I can not understand how the problem would be solved) I am not able to implement this particular behavior.

What would be the best way to follow the condition that I finally make this change?