Image sort order behaving oddly

AFAIK we don't have a way to sort images on a product however, it used to sort in the order I uploaded them. But I'm seeing odd sorting now. Based on the image IDs in the back end, I see 139, 138, 195 in that order. Shouldn't it be showing as 138, 139, 195? It's becoming very difficult to get the right main image to display and I can't tell my client to keep deleting and re-uploading until they get the one they want first.

Forgot to say, I'm on version 1.5.3 Business still

Hi,

Indeed, the sorting system for images wasn't really great with previous versions of HikaShop.
Since then we've added a sorting column to the images listing of each product so that regardless of the order in which you upload the images, you can sort them the way you want.
So I would recommend to update to the latest version.
I also recommend you to do a backup and to try the update on a copy of the website in case you have an issue with the update.