Chrome Plugin Manifest V3 - strange behavior of a promise function in popup.js

Question

I'm trying to create a small plugin to make my day-to-day job easier. I have faced a very strange situation within the popup.js script. The promise function randomly refuses to get executed. I have spent some hours trying to debug or at least understand where the issue could be but without any results.

Here is the skeleton of the code:

  document.addEventListener('DOMContentLoaded',  function ()  {
 // some initialization
 document.getElementById("signinbutton").addEventListener("click", function(event) {

 try {
        // some more initialization
        var user_email = '';
        var advertiserId = '';
        var checkibm = '';

        user_email = $('#emailfield').val().trim();
        advertiserId = $('#advertiseridfield').val().trim();
        checkibm = $('#checkibm').is(':checked');

        if (advertiserId && checkibm) {
            _act = 'getTokenIdByAdvId',
            _data = advertiserId
        }
        else if (advertiserId && !checkibm) {
            _act = 'getTokenIdByAdvId',
            _data = advertiserId
        }
        else if (user_email && validateEmail(user_email))
        {
            _act = 'getTokenIdByEmail',
            _data = user_email
        }
        else
        {
            throw new Error("Valid input has not been provided");
        }

        sendMessagePromise({
                act : 'getTokenIdByAdvId',
                data: '16910'//encodeURIComponent(user_email)
            })
        .then(responseHandler)
        .then(responseReplaceTokenHandler)
        .then(show_ok('Done'))
        .catch(failureCallback);

    }

    catch (error){
       //doing some error catching here
  });

});

The code above works perfectly. However, as soon as I fill in the real values in sendMessagePromise e.g

//_act and _data show the proper values when inspected
sendMessagePromise({
                    act : _act,
                    data: _data//encodeURIComponent(user_email)
                })

the flow skips execution of sendMessagePromise and any other chained function, except the last one ".then(show_ok('Done'))", i.e the only result is the "Done" message on the screen.

I made sure the values are correct. I'm able to debug step-by-step and see the values being properly supplied. I have also put a bunch of console messages inside the chain promise functions to see where the execution gets stuck, but it seems like it doesn't even start executing sendMessagePromise.

As soon as I replace expression back to hardcoded values i.e

            sendMessagePromise({
                    act : 'getTokenIdByAdvId',
                    data: '16910'//encodeURIComponent(user_email)
                })

it starts working again. I'm really stuck and not sure how to debug or which steps to take further.

Please assist