The bug
Some entities are rendered black if there is no light near them. This can be easily reproduced in the End.
Affected entities (1.11)
Minecarts with
DisplayTile, such as hopper minecartsWet wolves
Primed TNT
Code analysis
Based on 1.11 decompiled using MCP 9.35 rc1
The renderer of all affected entities call the method net.minecraft.client.renderer.BlockRendererDispatcher.renderBlockBrightness(IBlockState, float).
Can confirm (see screenshot), and in case anyone else wants to confirm it, you'll need this code for spawner minecarts (note: /give will not work):