Hey guys, not sure how to go about checking if this works in a battle, but I found what is at least a minor visual glitch in teambuilder. I was using it to calculate IVs of my pokemon in game, and after messing around I noticed that the "Suggested Spread" gave me different results if I set a Pokemon to really low levels as opposed to lv100. I put in a Volcarona with Fiery Dance, Bug Buzz, Roost, and Quiver Dance at level 1, and the suggested spread gave me negative EVs in special defense.
There was a negative placed before the number in special defense, as well as a minus and plus for a nature pertaining to different stats, and if I changed it to a neutral nature and set all other counters to zero, it would say I had 632 EVs to use for Volcarona. I've left teambuilder and returned to see it still reading SpD as -124, but the slider remains at zero and SpD has still been lowered. This also working in a similar manner for an Alakazam using all attack moves, and it gave me negative Attack, which could be abused if it's allowed in battle. It should also be noted, I know that it won't allow me to do this manually, because anytime I put in the minus it changes the nature, but in this case I can at least use a neutral nature and the negative value is still there. I was also able to change it to any Pokemon and still see the same negative number.
After testing a little, the Volcarona only does this with the particular IVs that were set to it, being 24 30 15 25 21 17 respectively. Full 31s in everything don't cause this