Note: this is the current experience for logged-out users on legacy vector

There is a gadget running on old Vector but not Vector 2022.

They are identical when all gadgets are disabled:
https://commons.wikimedia.org/wiki/File:%22Everything_is_Going_to_be_Alright%22_artwork,_Christchurch_Art_Gallery,_Christchurch,_New_Zealand.jpg?useskin=vector&safemode=1

In T305630#7838353, @Jdlrobson wrote:

There is a gadget running on old Vector but not Vector 2022.

They are identical when all gadgets are disabled:
https://commons.wikimedia.org/wiki/File:%22Everything_is_Going_to_be_Alright%22_artwork,_Christchurch_Art_Gallery,_Christchurch,_New_Zealand.jpg?useskin=vector&safemode=1

And it seems like this is a default gadget?

Looks like it. A Commons admin should be able to easily work out what to do here. Note, that the file table of contents has nothing to do with the one we're working on in the sidebar. The file table of contents is something different and a completely different code path.

I suggested to Olga that we reach out to Commons Village pump and enquire about getting this script loaded on new Vector.

https://commons.wikimedia.org/wiki/MediaWiki:Gadget-Stockphoto.js#L-40 tests for skin support, so it's not loaded on New Vector after the variable was changed.