asp.net: Postback disabled after validation failed - asp.net

Question

After validation failed, I have a problem with controls (dropdownlist or button) that should cause a new postback. I will try to explain it clearly...
The purpose of my page is to save fives dates in a database. The page has the following controls:
Five textboxes, each one containing a date
A reset button (CausesValidation=false) to restore a default date in one of the 5 textboxes
A dropdown list (AutoPostback=true, CausesValidation=false) of predefined templates that applies 5 dates to the 5 textboxes
A button to save the dates to the database
The textboxes can be edited manually. So, when I click the Save button, if the format of the dates is not valid, the validation fails and the save is aborted. The problem is just after that. If I click on the Reset button or select an item in the dropdownlist, the postback is not triggered. If I try again, then it works. Is there a way to make it work the first time after the first validation failed? I tried deactivating the validation on the client-side when changing the selection in the dropdownlist but the postback still does not occur.
Here is the relevant part of the code:
<asp:DropDownList ID="cboScheduleTemplates" runat="server" AutoPostBack="true" CausesValidation="false" />
<asp:TextBox ID="txtDateDelivery1" runat="server" />
<asp:RegularExpressionValidator ID="revDateDelivery1" runat="server" Display="Dynamic" ValidationGroup="Schedule" ControlToValidate="txtDateDelivery1" Text="*" />
<asp:TextBox ID="txtDateYearbookQuantity" runat="server" />
<asp:RegularExpressionValidator ID="revDateYearbookQuantity" runat="server" Display="Dynamic" ValidationGroup="Schedule" ControlToValidate="txtDateYearbookQuantity" Text="*" />
<asp:TextBox ID="txtDateDelivery2" runat="server" />
<asp:RegularExpressionValidator ID="revDateDelivery2" runat="server" Display="Dynamic" ValidationGroup="Schedule" ControlToValidate="txtDateDelivery2" Text="*" />
<asp:TextBox ID="txtDatePersonalizations" runat="server" />
<asp:RegularExpressionValidator ID="revDatePersonalizations" runat="server" Display="Dynamic" ValidationGroup="Schedule" ControlToValidate="txtDatePersonalizations" Text="*" />
<asp:TextBox ID="txtDateDelivery3" runat="server" />
<asp:Button ID="btnSetDefaultDelivery3" runat="server" ValidationGroup="Schedule" CausesValidation="false" />
<asp:RegularExpressionValidator ID="revDateDelivery3" runat="server" Display="Dynamic" ValidationGroup="Schedule" ControlToValidate="txtDateDelivery3" Text="*" />
<asp:Button ID="btnSaveSchedule" runat="server" CssClass="btnAction" Text="Save" ValidationGroup="Schedule" />
<asp:ValidationSummary ID="validationSummarySchedule" runat="server" ValidationGroup="Schedule" DisplayMode="List" />

Answer 1

As suggested in this post, the problem comes from calls to Page_ClientValidate. So I wrapped the client function like this and the problem went away:
function DoPageClientValidate(validationGroupName)
{
var result = Page_ClientValidate(validationGroupName);
Page_BlockSubmit = false;
return result;
}