Contextual Filters (in Child View) not working after PHP upgrade

Problem/Motivation

So we have recently upgraded the PHP version into PHP 8.0 (our Drupal version is Drupal 7.67). We have these 2 Views (Let's call it View 1 and View 2) and inside View 1's Fields list, we added another child View (Let's call it View 1a).

We noticed that the Contextual Filters value that we passed from View 1a into View 2 are somehow not passed (from View 1a) or not received from the other View (View 2). We know this because when we create a page to show just View 2 and pass a hard-coded Arguments parameter into it, the View data are shown properly. While if it is from the View 1a's preview, the data is empty.

The worse thing here is that there is no error message shown (even when the debugging mode is activated) and no useful info from the logs as well.

Wondering if there is anyone who experienced similar issue or knows what to do/how to solve this.

Regards,

Frans