Thank you for sharing the code, it was critical to discovering the problem.
Please put aside a few minutes to carefully read this article which explains the issue and provides a couple solutions - Troubleshooting: Controls are not Appearing. In your case, the StackLayout at the root is breaking UI virtualization (the "not enough room" problem).
Just remove the StackLayout. Since you already have a Grid, and the RadListView is in the star-sized RowDefinition, that's all you need for the root element
Note: Although a redraw when orientation changes temporarily resolves the issue, it's a lucky coincidence.
If you have any further trouble, please open a Support Ticket so we can assist. A forum thread doesn't carry a guaranteed response time like your Priority Support license has. Although not relevant in this case because you have a GitHub repo, you can attach ZIP files with your code to a ticket.
We do our best to answer forum posts in a timely manner, but this is limited by current workload and can take a few days at worse. Whereas a Support Ticket is always answered within the ticket's timeframe.
Lance | Manager - Technical Support
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