URLs of cached thumbnails are same if there is a dot in image path:
create article with image /images/201718/Summer_1/18.5/image1.jpg
create 2nd article with image /images/201718/Summer_1/18.5/image2.jpg
Load module - see that two articles are displayed with same image. The JAImage::resize() method doesn't use normal code to detect the filename (pathinfo()) but splits the path on first dot - it's really weird, this developer should learn PHP.