[BUG] Random Entity Textures don't work on minecarts

[dhsddaniel]

While testing my resource pack with the ETF mod, I noticed that minecarts don't render correctly. While they do comply to the Custom Entity Model, they don't appear in random textures, but always use the default one located in the assets\textures\entity folder. Due to this misbehaving of the mod, the minecarts now look broken, because the original file is using a different aspect ratio compared to the intended one(s).
Up until now, I used OptiFine for using the resource pack, which worked fine. Random textures on any other entity than minecarts work fine however. No matter how hard I tried to fix it, it didn't work. I have no other mod than ETF installed. Minecraft version is 1.21.1 and ETF version is 6.5.2

You can test this out by downloading the resource pack in question: https://map.minedorf.de/MinedorfPreSept24-2.zip

This is how it is supposed to look like:

This is how it looks using ETF:

log

There are no logs indicating what is wrong.