Hi Teemee Tang,
Thanks for using Syncfusion product.
We have analyzed the reported issue, and it works fine from our side we have tested the same with multiple layouts (Content page, navigation page, Grid) and it works fine. We suspect that you may host calendar inside the stack layout, which may cause the issue, it’s stack layout’s behavior. Kindly use any other layouts and if the issue remains same kindly revert us back. We have prepared a simple sample for the same.
Kindly revert us back if you have any concern.