Okay, I've come across another odd error that doesn't seem to make sense, I make items alot, all sorts of fun tricks.. and from my logic this should work, or more accurately shouldn't give the error. "You can't use it that way." there doesn't seem to be any gating on use of this object after all

The potion simply turns the player into an animal(commented out the species/cloning aspects for testing when it first didn't work

 <object name="Feral Potion">
        <inherit name="editor_object" />
        <visible />
        <look>Its a potion with  a bright green and orange mixture  inside, a cork stopper. On the glass are four small pawprints..</look>
        <feature_usegive />
        <alias>Flask with Pawprints</alias>
        <take type="script">
          AddToInventory (Feral Potion)
          // CloneObjectAndMove (Feral Potion, player)
          msg ("You take the flask in one hand and feel a strange tingle in your spine, visions of something primal dart through your mind a moment")
        </take>
        <use type="script">
          SetObjectFlagOn (player, "feral")
          msg ("You become a feral {player.species} (placeholder desciption)")
          // player.species = "Feral" + player.species
          SetTimeout (160) {
            msg ("pain races through your body again, your sprawl out on your stomach as your body shakes..and your returned to an anthro shape...")
          }
          RemoveObject (this)
        </use>
        <givesingle type="boolean">false</givesingle>
      </object>

Maybe try looking at the use command? Something may be wrong there.
Everything else looks fine.

It was really strange,I literally copied over another very similar potion to another item name, then copy pasted the scripting, and that fixed it.. almost as if that one item had got some little attribute mixed up...

Edit...well this is a turnip for the books, the "Problem" was the alias, changing it to Pawprint Flask made it work fine.. must have been the "With" part of the name that was confusing the program

Quest has a USE #object1# WITH #object2# command; it must have matched that first, matched your object to both objects, then reported that you cannot use the flask with the flask.

Mhmm. Its kinda what a Figured once I narrowed down things, sort of the facepalm of realization that i seem to do alot when I code stuff.

Seems confusing