I finally decided to uninstall this plugin for which I paid a huge 99$ amount.
Although I knew for some time already, that it was no more actively supported, it was apparently working on my website.
However, following several page speed tests, I recently discovered that the generated sliders are not leveraging wordpress thumbnails, and instead, are loading the images in original size, thus reducing tremendously the page loading size !
Of course, since there is no developer working on it anymore, I have no hope of having this issue fixed.
Having looked for an alternative in the plugins library, I found another one which does the job perfectly, is actively supported, and only costs 24$.