Heres a way to test it. Get spinel to have 5 debuffs.
1.Go find a random monster
2.Use a space on him. Keep an eye on the mark thing from your space.
3.Now tell spinel to use the 5 debuff on the target.
When she applies the 5th debuff you will notice the mark will disappear even though your space hasn't timed out yet. It's sad too cause I had to limit my guardian debuff to prevent it from interfering with my space
Note that glacier, deadly fen, electro attack is a debuff too. Maybe that's your problem even if your spinel has 4 debuff.