order of additional images changes when upodated

For example, I have 5 addtional images under one product, in the product edit page, I click save buttom,
the first image will be in the last position and the last one will be moved to the first position.

I am if get back to product edit page,

Ok, I am having the same problem.
Whenever I edit (or not edit anything but just re-save) a product, the order of the additional images gets all mixed up. I tried to check if the problem could be with the filename of the images (numerals, Uppercase etc...) but that's obviously not the problem.

I'm running OC 1.32 with the Excel Export/Import Plugin installed.
Anybody else has the problem? Any ideas how to solve this?