onblur event fires only on alternate input fields in Firefox

Question

After each form input element, I need to do a verification using the same script.
I used onblur=myFunction("name") (where nam e is the name= attribute for the form field) in each form element so when the user presses <tab> the cursor advances to the next entry field.

The problem is that Firefox (Linux 93.0 - 64 bit) fires the onblur event ONLY on odd-numbered form input fields. The even numbered ones lose focus without executing the event handler.
Sometimes, but not always, I can force the event to fire by clicking on a different form input field, or rotating out and back into the form. This is very consistent.

Here are two example sequential fields from the real form, ' fname ' fires the event, ' lname ' does not.
There is a total of 17 named input fields. The style for these fields does not reflect the "unfocused" state after the cursor exits the field either.

<label for="fname" class="shipping">First Name</label>
<input type="text" class="shipping" name="fname" id="fname" maxlength=24 size=20 placeholder="First Name" autofocus onBlur=field_check("fname")>
<label for="lname" class="shipping">Last Name</label>
<input type="text" class="shipping" name="lname" id="lname" maxlength=48 size=30 placeholder="Last Name" required onBlur=field_check("lname")> 

How to fix this issue?

Answer 1

Thank you to those who responded, even though nobody had an answer. I did a lot of testing and found that the problem is interference between the CSS styles and the inline onBlur, onChange, etc. When these are removed all works as expected although I can no longer determine when a field has been completed. Testing, I found that Firefox (Linux and Windows) will respond to every second event, so alternate lines do not get styled and do not report data entry. Chrome on Windows will hang after the third field is entered and the pop up cannot be dismissed without closing the browser. An old version of Internet Explorer (!) worked exactly as expected but I couldn't test either Edge or Safari since I don't have them installed here.
Overall, there seems to be some disconnect between the documentation and the implementation on mainstream browsers but I have run out of time to try and find it so I'll have to find a "plan B".