Android 5.x: Why does Dialog.Builder cuts text off?

Have you tried using Dialog instead?

final Dialog dialog = new Dialog(context);
dialog.setContentView(R.layout.custom);
dialog.setTitle("Title...");

// set the custom dialog components - text, image and button
TextView text = (TextView) dialog.findViewById(R.id.text);
text.setText("Android custom dialog example!");

// make 3 buttons instead of one
Button dialogButton = (Button) dialog.findViewById(R.id.dialogButtonOK);
// if button is clicked, close the custom dialog
dialogButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
    //do something
    }
});

dialog.show();

recommendation: use linear layout for the dialog.