Success/error Messages not closing after 2.3.5 update

[theranicho5d45]

Hello Magento Community.

Ever since my upgrade from 2.3.2 to 2.3.5 I'm having a problem with the success/error messageboxes when, for example, you add an item to the cart. They popup fine, but I can't close them. Both the cross button and the 5 second timer are not working. Lets make one thing clear though; I've been reading other threads with people having the same problem saying that the messagebox stays when going to another page, but this is not the case for me. After I leave the page or refresh, they do disappear.

So I've tried the following things:

• Disabling full page cache
• Tried the messageboxes on every page, yet I get the same results no matter where I use them, So its not page-related.
• Debugging in message.js

So, I've been logging to the console in every function in the message.js file. The function where the 5 sec timer gets activated does not even trigger at all unless I call it in the 'initialize' function myself. Lets look at the function that I'm talking about:

        onHiddenChange: function (isHidden) {
            var self = this;

            // Hide message block if needed
            if (isHidden) {
                setTimeout(function () {
                    $(self.selector).hide('blind', {}, 500);
                }, 5000);
            }
        }

So, just like I said, I called it myself and it does run. However, the boolean 'isHidden' never turns to true, so the timeout never gets activated. So I commented that out aswell, but then my logs do get called, but still, the message never disappears. The timeout works fine but the 

$(self.selector).hide('blind', {}, 500);

 doesn't.

I think its rather a global problem in Magento instead of just the messages, since I'm also using a Mollie plugin for Magento which uses a javascript timer aswell. The plugin works fine but the timer doesn't. After chatting with the creator of the plugin we got to the conclusion that its a problem in my Magento rather than a problem in his plugin and I guess its has the same roots as the message problem.

I've read something about JQuery-UI changes in 2.3.5, but AFAIK these are just reference changes which will affect only performance, correct me if I'm wrong.

I have no clue at this moment. Hopefully anyone can help me out or atleast push me in the right direction.

Thanks in advance!