It should be /wp-content/uploads/sites/SITE_ID/ actuall
So it should be like the first network which does have that structure, right?
That may be a problem, then, because if the 'image' had a poorly done install of WP, that would explain a lot.
The weird thing is that that poorly installed WordPress did behave normally until I added networks...
The thing I don't get is why the second network and the third behave in very different way... If the install of the first network is somehow corrupted (but still gives the expected results as far as image upload path is concerned) and it is used as some sort of template for the second and the third then why do I end up with verrry different things for the second and third network? I end up with blogs.dir for the second network and something similar to one of the problems you had for the third network (/wp-content/uploads/sites/25/sites/26/...) because the upload_path got set for the sites of this network automagically.
(It's 25 now instead of 23 as I destroyed the network and recreated it and the new upload_path is wp-content/uploads/sites/25...)
The third network appears to behave similarly to the first network with the exception that this time the upload paths got set... If I cleared them then I think it would behave normally but why did they get set in the first place?
That said, NEVER use an 'image' to install WordPress. It prevents WP from being able to auto-detect and properly set things up.
I definitely learned my lesson and I wished I could restart with a clean database... If I exported everything with EXPORT, IMPORTed it back in a clean database and altered the path to the images would this have a better chance of ending up with a working install which would not do something else weird the next time I create another network?
I could hack my config as you suggested but what I am afraid of is keeping that corruption which makes it behaves differently each time I create a new network so if exporting and importing into a new database has a better chance of getting rid of the "corruption" then I would go that way.
The second network has barely any images so I could re-upload them or I could move them from their incorrect location to the correct one too and the third network was only done as a test for now...
So, what would be best in my case?
Thank you very much for your help and have a nice day!