the user_reg_date needs to be a timestamp value with a default value of CURRENT_TIMESTAMP. And you should leave the value empty.
for the user_password field you might want to remove the WA_encryption and replace that with the crc32 hash if that is what is required -
<?php echo crc32 (((isset($_POST["password"]))?$_POST["password"]:"")); ?>
for the username_clean and the user_email_hash try removing the strtolower and just using crc32.