form toolkit should not be added to page that already has validation toolkit applied to it, the existing validation and validation show if behaviors from validation toolkit should be removed from the page, then recreated using form toolkit.
to have the valid form elements retain the values on validation failure, bind the initial value of each form element to the corresponding binding in the Validated entries collection.
Select each form element in design view, then click the Lightning bolt next to initial value in the property inspector, in the Bindings panel, expand the validated entries collection and select the corresponding binding.
The errors are store in a session variable, if the validation fails the errors will be displayed on the page if the users browses away and comes back until the form is successful submitted.
to prevent this from happening, you can add the following code after the closing </html> tag:
<?php unset($_SESSION['WAVT_enquiries_Errors']); ?>
please send a copy of the page so i can look into why the captcha error shows when file size validation fails.