I've been using Magmi to do a mass import of both product data and then going over the product data to reference product images via SKU. I've been able to get Magmi to import product data without issue, but have hit a snag with the image import.
Thing is, I've gone through some 10,000 products and was able to assign images to most of them against another CSV containing the product SKU and assigned images. And for a lot of the products, the base image, small image and thumbnails have been correctly assigned and show on the front-end.
However, there are still a significant amount of products that are not showing the small image and thumbnail on the front-end despite having the images assigned in the backend. I've been working most of this day going through reindexing, resetting the product images by overwriting the product data with blank images and redoing the image import, to messing around with the profile settings to see if it is something to do with the configuration.
The header of my image import CSV is as follows:
"sku", "image", "small_image", "thumbnail", "attribute_set", "type", "store", "product_websites", "visibility"
I'm not sure if I'm missing a specific needed field in which I must set in order cover all products on the update, since adding the visibility field seemed to work in getting most of them to display. Most, but not all unfortunately, and so far, the only way I can get a product that has been assigned an image via import to display all the images on the front-end is to manually edit it (set it to no image and then set it back). If I can solve this for the automatic import, then it'll save my client having to go through amending the images manually.
To note, I've made sure to reindex, clear cache, tweak configuration, over and over, whilst checking various support thread both on Stack Exchange and on other forums. So far, no success!
EDIT Nevermind, the solution is simple. Go nuclear and clear the whole catalog and reimport afresh. Images then uploaded and were assigned without issue. Tears of joy...