I get this error log after installing RebornCore with RandomUitlities: https://paste.ee/p/6j2oj

Thanks for that

Mind sending me a link to the mod?

Ok, so looking at their source, core modding this has broken some stuff. I will see if I can do it without core modding.

they are overriding TileEntityItemStackRenderer.instace here: https://github.com/61352151511/Random-Utilities/blob/55e5839c8276184d29a3d8f971a8072422b036b9/src/main/java/com/sixonethree/randomutilities/proxy/ClientProxy.java#L69 I could beat them to it, and add special support for them