I wanted to create some particle auras around mobs that also applied some area effects when you got close to them.
I found that potion and status effects assigned to the entity would not apply to players standing within their hitbox (confirmed using F3-B) IF the entity was riding another one.
As soon as I killed the entity they were riding the potion or status effects would immediately start applying to me. The same AreaEffectCloud entity data summoned without riding another entity applied the effects perfectly so this seems to only be an issue when the effect cloud is riding something else.
It would be nice if this could be fixed and effects could be stored in the riding effect clouds as it creates a nice mobile version of the AreaEffectCloud entity. Right now I have to use /execute and /effect in a seperate command block to get around the bug which introduces unneeded lag.
Never mind. This was a product of the fact that I was setting the Age of the clouds back to zero when they were near their carrier so they would remain persistant only until it died. Apparently AreaEffectClouds will not apply effects when their age is zero regardless of other data. I put the age reset on a once a second cycle and the effects applied perfectly at ages above 1. So it's just a built-in cooldown I think after creation.
Issue resolved--at least for my purposes. I assume this is intended behavior?