Magnifier plugin changes main thumbnail image size!

i mean the link to orginal image changes to the 50×50 px image for some products like this:

https://shop.ifnam.com/product/%D8%B9%DB%8C%D9%86%DA%A9-%D8%A2%D9%81%D8%AA%D8%A7%D8%A8%DB%8C-%D9%87%D9%88%DB%8C%D8%A7-hoya/

and works fine for some like this :
https://shop.ifnam.com/product/%D8%B3%D8%A7%D8%B9%D8%AA-%D9%85%DA%86%DB%8C-%D9%88%D8%A7%D9%84%D8%A7%D8%B1/

at first sight the two links you provide seem having the same behaviour