Additional Details/Testing methodology:
This happens regardless of RTX resource pack used.
You can use the empty-rt-capable-rp.mcpack I’ve attached to enable ray tracing in any world (which loads vanilla resources exclusively)
It appears game’s spritesheet/texture atlas is leaking into the Hopper texture on minecarts.
This issue was not present prior to some recent technical changes Mojang made to texture atlases.
Other minecarts are not affected, only Hopper part of Minecarts with hopper.
Other notes:
Resource pack authors may be able to work around this issue by defining a custom geometry for hopper minecarts, and manually modelling the hopper inside of Minecart.
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