Thank you for the attached code snippets and images, which shows the issue.
We tested the case on our side while using the latest version of UI for Nativescript plugin 3.0.4, however, the ListView was rendered properly on both Android and iOS and we were unable to find any difference.
Could you update the plugin's version to latest available one and to rebuild your project. Bear in mind to remove node_modules and platforms folders, before rebuilding.
If the problem still exists please review the attached sample project and make the needed changes, which will allow us to recreate this scenario.
Also for further help, you could review the horizontal scrollDirection example here