If the checkbox checked property is not correctly chosen even though it is already been set in the client side programming that is because the property must not been included if the value is false. So make the check box with condition if the value is false then not include the checked property. The code will be like below:
<% var.value == true ? 'value=true checked=true' : 'value=false' %>
Hope this will solve your problem, if you still need help then just post in the comment, i will help you as soon as i can.