Button needs to be clicked twice to trigger btnSaveEvent() in VB.net

I have a form on web application, I load the field values on the form and click the save button and it doesn't save the record on the database at first click but if I press the button again it saves it. I put the breakpoint on my Page_Load()event and tried debugging it so what happens is as I run the application, Page_Load() gets executed populates the data on the grid. Now, if I enter field values and click save, it again goes to Page_Load() event but it doesn't go to button_save() event. But if I click it again then it goes to Page_Load() and then goes to button_Save() and saves the record.

I want to click the mouse button once and save the record, how could I be able to do that? I am using VB.NET. Thank you.