Eternatus VMAX bug when knocked out

muTTni

I had 5 Pokémon in my bench as my Eternatus VMAX was knocked out. Why was I forced to discard one Pokémon from my bench? Ability reads "If this ability stops working, discard until you have 5."

If I had 6 Pokémon in play, (Eternatus VMAX in my active and 5 on my bench) why was I required to reduce my bench size to 4 cards?

I was forced to discard one of my five benched Pokémon before being able to place a new Pokémon into play.

TechHog

What were you playing against?