Changing Payment Method (Error - Help!)

This started this morning and I have no idea how to fix it or what caused it in the first place:

When you change a payment method during checkout the following error happens:

https://------site------.com/js/lib/creditcardvalidator/jquery.creditCardValidator.js?ver=1628442809@281:21

Uncaught TypeError: Cannot read property ‘replace’ of undefined

TypeError: Cannot read property ‘replace’ of undefined
at normalize (https://------site------.com/js/lib/creditcardvalidator/jquery.creditCardValidator.js?ver=1628442809:281:21)
at https://------site------.com/js/lib/creditcardvalidator/jquery.creditCardValidator.js?ver=1628442809:276:18
at s.fn.init.$.fn.validateCreditCard (https://------site------.com/js/lib/creditcardvalidator/jquery.creditCardValidator.js?ver=1628442809:297:25)
at Function. (https://------site------.com/checkout/:1868:23)
at Function.trigger (https://------site------.com/var/cache/misc/assets/js/tygh/scripts-acf57d305bdbcc30d3ddfea8c684fc46.js?1628442809:1:271573)
at Function.e.ceEvent (https://------site------.com/var/cache/misc/assets/js/tygh/scripts-acf57d305bdbcc30d3ddfea8c684fc46.js?1628442809:1:334896)
at Function.commonInit (https://------site------.com/var/cache/misc/assets/js/tygh/scripts-acf57d305bdbcc30d3ddfea8c684fc46.js?1628442809:1:384083)
at Function. (https://------site------.com/var/cache/misc/assets/js/tygh/scripts-acf57d305bdbcc30d3ddfea8c684fc46.js?1628442809:74:30)
at Function.trigger (https://------site------.com/var/cache/misc/assets/js/tygh/scripts-acf57d305bdbcc30d3ddfea8c684fc46.js?1628442809:1:271573)
at Function.e.ceEvent (https://------site------.com/var/cache/misc/assets/js/tygh/scripts-acf57d305bdbcc30d3ddfea8c684fc46.js?1628442809:1:334896)

I don't even know where to begin to look to find what caused this to start happening?

Does the error occur for specific payment methods only?

We only have two options and it happens when you change between either. It's the only error on the entire site.

try to temporary create two additional payment methods and disable existent ones to test

I tried that...same problem...but ultimately found out it was a corrupted, very old addon that somehow caused an issue. Sent you a PM on something else though.