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Random doubles. Contrary Lurantis' defence got a boost rather than a drop when partener used Max Steelspike.
See turn 8: https://replay.pokemonshowdown.com/gen8randomdoublesbattle-1153337222
BUG STATUS: NOT A BUG, see urkerab's post below (DaWoblefet)
A display error of stats in the just-after-battle replay.
Manectric has +1 Spe and +1 SpA due to scarf and lightning rod.
Correct HP,Atk,Def,SpA,SpD,Spe should be 249,145,146,219,146,219 before modified, and 249,145,146,328,146,328 after modified...
I am wondering why Mega Gengar is ranked 'DoNotUse'. I've used it a lot and found it not bad on the ladder. Its advantages over Gothitelle are a higher speed, immunity to trick, and most importantly, access to curse. Those seem not to be that worthless. Especially when the opponent is not weak...