it seems that a fair number of folks are still having issues with crediting vendors & getting images to upload all at the same time. i just found this in the galleries that was posted today:

https://www.renderosity.com/mod/gallery/helpful-hints-on-vendor-credits/2642414/

[instructions/work arounds for the problem... maybe // posted by the helpful GrandmaT]

maybe this will help until it's addressed by the programmer[s].