The glowing texture on entities such as Spider, Enderman and Phantom does not have highest rendering priority. Some entities are displayed on top of the entity's glowing texture (even items on hand can be displayed on top of the entity's glowing texture while the entity itself does not).
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duplicates 1
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This one is partially a copy/duplicate of MC-218015, since my ticket explains about mobs, not other entities.
Mobs are entities, the comments even list the affected mob types.
Duplicate of MC-218015.
Does MC-218015 describe your issue?