Reset button clears all CSS

Hi guys,

Thank you for an AMAZING module. I have been using it since starting out on Drupal 7 years ago.
I am not sure if I marked this issue correctly. Please forgive me if I made a mistake.

I just created a webform with version 8.x-5.10 and added a reset button. I noticed that when I click on it, all my CSS styles are stripped from the form.

Looking at the HTML in Firefox's Inspector, I can see that the ID's of fields changed which means my CSS selectors are now not valid.

EG: Changing from id="edit-contact-details" to id="edit-contact-details--GAgAuvKClHU"

I need those specific ID as I am styling each fieldset's legend in a different color.
Am I doing something silly somewhere?

Any help would be much appreciated.