At first, I was hesitant to buy the premium version so I started with the free option.
After a while, seeing the quality of the plugin and the results I was getting, I decided to give it a shot and switch to premium. No regrets!
They have an amazing support team that is always there no matter how big or small your problem is. Do yourself a favor and stop using free plugins that kind of work and just buy whatever plugin you need from YITH.