Hi there!
I was reading your problem again and also my answer. Although that is the expected behavior, the camera will focus on the zoomed character or tile. But not always will be able to center it on the screen. That depends on what position the character is from the edges of the map. If it is too close of an edge, it may ended up looking like your result above.
If you experiment it with a very large map, and put the zoom on the player, walk through all the map and you will see that the player will be centered, as long as it is far from the edges. When he is getting closer, the camera needs to adjust so it not shows any black screen border.
Also, taking a look at your plugin command, the plugin version you are using seems to be outdated. Because the 1.3.0 had another argument inside the plugin command:
