We currently have various other reports on problems with the Product Gallery. However, I don’t know how to reproduce your specific problem, but I hope that it will “fix itself” as soon as the other - partly similar - problems are solved.
Does the same problem occur if you use the horizontal slider instead of the vertical one (i.e. the thumbnails are under the main image instead of next to it)?
Does the problem also occur with a completely new, unstyled element?
Does the problem occur if you set a larger image size in the elements settings?
Would you be so kind as to send temporary login credentials and a link to this thread to help@bricksbuilder.io using the email address you used during the purchase?
Hey, unfortunately, we have not been able to find the cause of the problem and cannot replicate it - however, we have added some custom JS, which fixes the problem in your case.
Maybe you can try again to reproduce the problem in a new, very simple installation (without xxx plugins and custom code).