Hi,
I have figured out the problem eventually. The problem is arising from how the scripts and styles of the plugins are enqueued. This causes them to be enqueued before the jQuery dependency, thus failing.
With hope that this will be taken into consideration for the future plugin versions, here are the changes made:
First of all, I moved all enqueues in separate functions to use the recommended wp_enqueue_scripts hook instead of the wp_enqueue_script currently used by the plugin.
Second of all, I added priority to all wp_enqueue_scripts hooks (in my case, 10).
Third of all, I transferred inline css style to a file and enqueued it in the same method.
I assume another option would be to check the jQuery dependency before enqueue or including jQuery if missing.
Have a good day!