top and left line border not showing on Android 7.0 - codenameone

Question

In my cn1-project, the top and left line border for Label, Button and TextField are not shown on an Android 7.0 device. The simulator shows all borders correct. The issue can be easily reproduced with the code from the SignatureComponentDemo on the current cn1 version 4.x for the themes FlatXXXX which also use line borders instead of border images.
I created a new FlatBlue "Get Started App" on Intellij Idea and replaced the code for init(), start(), stop() and destroy() in MyApplication by the code from the SignatureComponentDemo.
The TextField for the name in the demo shows correctly with a line border on the simulator. One the Galaxy S7 edge with Android 7.0 the top and left border of the TextField are missing. Adding more padding for these components has no effect. Also disabling loading of native theme by setting includeNativeBool to false has no effect. The only relevant code is in the following method:
public void start() {
if(current != null){
current.show();
return;
}
Form hi = new Form("Signature Component");
hi.setLayout(new BoxLayout(BoxLayout.Y_AXIS));
hi.add("Enter Your Name:");
hi.add(new TextField());
hi.add("Signature:");
SignatureComponent sig = new SignatureComponent();
sig.addActionListener((evt)-> {
System.out.println("The signature was changed");
Image img = sig.getSignatureImage();
// Now we can do whatever we want with the image of this signature.
});
hi.addComponent(sig);
hi.show();
}
Is there a workaround for this issue? I need to build a table of Components using TableLayout. The table class is no option, because i need to draw borders of different color and thickness and wanted to apply these to the Containers and Components within the container using TableLayout as a layout manager.