Why updates need a step
Every ox_inventory release ships its own web folder with its own built interface. Installing an update therefore replaces the redesign with the original look.
After you update ox_inventory
Put the redesign back by repeating the Installation steps: replace the web folder with the redesign, copy your own item images, and restart the resource.
Keep a copy of the redesign folder, including any changes you made to its look, so you can put it back after each update.
If the interface stops working after an update
The interface and the Lua side of ox_inventory exchange messages. If a new ox_inventory release changes them, the redesign needs a matching update.
The redesign is tested against ox_inventory 2.47.9. Check the Changelog for a newer release, or ask in the Discord. Until then, use the web folder that came with your ox_inventory release.
Going back to the original interface
Restore the web folder you backed up during installation, or copy the web folder from an official ox_inventory release of the same version, then run ensure ox_inventory.