OK, If you want to see the code, here it comes. Not sure how much it will help, tho...  

Start your code here:

add_filter('frm_validate_entry', 'validate_my_form', 20, 2);
function validate_my_form($errors, $values){
if ($values['form_id']  == 7){
	$email = wp_eMember_get_user_details("email");
	include "/home/customer/www/nepta.com/public_html/mysql_connect.php";
	$recital = $_POST['item_meta']['448'];
	

// if today is between Jan 1 and before March 2, renew date must be lastyear-0101 thru lastyear-09-30
	// If today is betweeen Oct 15 and Dec 31,t then renew date must be thisyear-0101 thru this year-09-30
	$today = date("Ymd");
	$thisyear = date("Y");
	$lastyear = $thisyear - 1;
	$JanDate = $lastyear . "-01-00";
	$OctDate = $lastyear . "-10-01";
	$JanDate2 = $thisyear . "-01-00";
	$OctDate2 = $thisyear . "-10-01";
	
// Set and check deadlines
	$dlj1 = "20221211";
	$dlj2 = "20221225";
	$dlint1 = "20230101";
	$dlint2 = "20230108";
	$dlcomjz20 = "20230115";
	$dlens = "20230305";
	$dlsen = "20230208";
	$dlfrei = "20230319";
	$dlham = "20230326";
	$dladult = "20230305";
	$dlhalloween = "20221006";
	$dlmushope = "20221023";

//Get date parms here
    $today1 = date("md");
	
	$roger = "About to call editdata";
	
include "/home/customer/www/nepta.com/public_html/members/editData.php";	
	
	// Set and Check Oversubscription

include "/home/customer/www/nepta.com/public_html/members/teacherchk.php";	
	
	
	// Return Errors 
	
	if ($deadline == "Y") { 
		$errors['deadline'] = '<strong style="font-size:1.1em;">The deadline for this application has passed</strong>';
	}
	if ($overlimit == "Y") {
		$errors['overlimit'] = '<strong style="font-size:1.1em;">You have already reached your student limit</strong>';
	}
	
} // end form id = 7
	// echo "Error: " . $errors['deadline'];
	return $errors;
}

Thank you for all your input. So, I deactivated the 2 snippets that were using the same function (frm_validate_entry) and it worked fine. So, now that we've narrowed down the problem, how do I activate these 2 snippets and be sure they all work? I have already shared the snippet in question. I will display the other 2 below and perhaps one of you can see my error. 

add_filter('frm_validate_entry', 'validate_username6', 20, 2);
function validate_username6($errors, $values){
if ($values['form_id']  == 6){
	$dbc = mysqli_connect (DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);
//Check connection
if (mysqli_connect_errno()) {
    echo 'Could not connect to MySQL: ' . mysqli_connect_error() ;
}
mysqli_select_db ($dbc, DB_NAME );
$memberdb = "wphq_wp_eMember_members_tbl";
	
	$user = $_POST['item_meta']['765'];
	$email = $_POST['item_meta']['173'];
	
	$check = mysqli_query($dbc,"SELECT * FROM $memberdb WHERE email = '$email'");
	$rowcount = mysqli_num_rows($check);
	if ($rowcount != 0) {// email has been found - error
		 $errors['my_error'] = 'This email already exists.';
	     return $errors;
		 }
	$check = mysqli_query($dbc,"SELECT * FROM $memberdb WHERE user_name = '$user'");
	$rowcount = mysqli_num_rows($check);
	if ($rowcount != 0) {// user name has been found - error
		 $errors['my_error'] = 'This user name already exists.';
	     return $errors;
		 }
  }

}

/* Validate email address exists  */
add_filter('frm_validate_entry', 'validate_email27', 20, 2);
function validate_email27($errors, $values){
if ($values['form_id']  == 27){
	$dbc = mysqli_connect (DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);
//Check connection
if (mysqli_connect_errno()) {
    echo 'Could not connect to MySQL: ' . mysqli_connect_error() ;
}
mysqli_select_db ($dbc, DB_NAME );
$memberdb = "wphq_wp_eMember_members_tbl";
	
//	$user = $_POST['item_meta']['741'];
	$email = $_POST['item_meta']['772'];
	
	$check = mysqli_query($dbc,"SELECT * FROM $memberdb WHERE email = '$email'");
	$rowcount = mysqli_num_rows($check);
	if ($rowcount == 0) {  // email has not been found - error
		 $errors['my_error'] = 'This email does not exist.';
	     return $errors;
		 }
  }
}

1. add_filter('frm_validate_entry', 'my_one_badass_validation', 20, 2);
2. function my_one_badass_validation($errors, $values) {
3. switch ($values['form_id']) {
4. case 6: // validate username in form 6
5. // do stuff
6. break;
7. case 7: // validate subscription in form 7
8. // do stuff
9. break;
10. case 27: // validate email in form 27
11. // do stuff
12. break;
13. }
14.  
15. return $errors;
16. }