& mini deer too. Are you talking of deers upon whom you can't cast spells or spells that turn their set to default?

Then they are necesserely wearing the Devotee or Crying Idol pelts.

Or sometimes there's a shapeshifted deer or a deer wearing the pelts above who is hidden between you and the deer you casted on, and your range get's pulled to the nearest deer, making it seem like it was the normal deer who repelled the spell.

What are they wearing, what do they look like, and what size are they?

You know, when i had the earlier version of TEF When i was a newbie and i didnt know what was going on, the deer in the forest, (some of them) HAd this weird all white pelt like a white silloutte and i thought it was a pelt spell X3

It's possible they have turned off visible players from the options. When you do that, nobody can cast anything on you.

Either that, or they have slow internets, meaning when you cast upon them, it might take a while for the casted spell to show up.