Image repeater – images vanishing after saving

Hello,

I’ve been using this plugin in a website for more than four years and it worked great until now. I have an image repeater field. I can add and upload images without any problem. However, when I save the posts, some of the images vanish without any reason. Sometimes all the images disappear, and sometimes only a few (even if I do the test with the same pictures).

Any idea of what can be the problem and how to solve it?
Thank you very much in advance!