Illegal invocation at elementClosest fullcalendar v4.3.1

I'm using fullcalendar library v4.3.1 inside a Salesforce LWC. All was working good in sandbox until I clicked inside an event and I get the following error:

aura_prod.js:999 Uncaught TypeError: Illegal invocation
throws at https://mybts--partial.sandbox.my.site.com/....../fullcalendar/packages/core/main.js:126:30 TypeError: Illegal invocation
    at elementClosest (main.js:126:30)
    at DateComponent.isValidDateDownEl (main.js:4070:25)
    at DateClicking._this.handlePointerDown (main.js:1128:57)
    at applyAll (main.js:988:36)
    at EmitterMixin.triggerWith (main.js:3523:17)
    at EmitterMixin.trigger (main.js:3518:18)
    at HitDragging.handlePointerDown (main.js:988:35)
    at applyAll (main.js:988:36)
    at EmitterMixin.triggerWith (main.js:3523:17)
    at EmitterMixin.trigger (main.js:3518:18)

I've tried many times what I've found on other threads (for example: https://github.com/fullcalendar/fullcalendar/issues/4990). Many people has shared this solution:

At core/main.js line 126 change this:

function elementClosest(el, selector) {
  return closestMethod.call(el, selector);
}

To this:

function elementClosest(el, selector) {
 return el.closest(selector);
}

But that solution doesn't work for me. As I upload the library to the static resource with that change I get a loaded error and the fullcalendar library is not loaded as it can load the core/main.js.

I've tried also with other versions and I don't make it work. Anyone can assist?

Change from a version to another.

SOLUTION: I’ve managed to get this works. I just realised I was not setting the path static source correctly.

I confirm this solution works for the fullcalendar library inside a lwc.

Change to this at line 126 of core/main.js:

function elementClosest(el, selector) {
 return el.closest(selector);
}

Then, you’ll probably have to do the same with function elementMatches() just below function elementClosest(). I had to do it and it worked:

Change this:

function elementMatches(el, selector) {
 return matchesMethod.call(el, selector);
}

To this:

function elementMatches(el, selector) {
 return el.matches(selector);
}