Hi, so i'm suddenly getting this error for some reason.. It was all working fine until today... :

Failed to load mods: Error while running setup for entity prototype "iron-chest" (container): next_upgrade target (steel-chest) must have the same bounding box.

Any help would be much appreciated... Thanks!

While it is true that my mod sets data.raw.container["iron-chest"].next_upgrade = "steel-chest", which is half of what your error message is reporting, in the base game the bounding boxes for iron-chest and steel-chest are the same.
You must have another mod installed that is changing the bounding box size of one of these chests, and not the other, which (combined with what I did) is causing the error to show up.

Ok then, thanks for the help man!

Edit: found the culprit, AAI Containers and Warehouses mod

Edit: found the culprit, AAI Containers and Warehouses mod

AAI actually has several compatibility issues with my mods.

Haven't had any other compatibility issues while running your mods and AAI until today, so i found it strange..

Haven't had any other compatibility issues while running your mods and AAI until today, so i found it strange..
Hello, may I ask you, how did you fix this issue?

Edit: found the culprit, AAI Containers and Warehouses mod

Thank you LittleDeath and Bobingabout, I had that same problem, and the same fix worked.