Spells like Inner Focus make spell casts cost 0 mana, which means they don't put you back into "while casting" mode. The LUF mp5 ticker still kicks in though - it shouldn't.

Maybe add a check for spell mana cost, and don't reset the ticker if it's zero? Or trigger the ticker when mana available drops (assuming max mana stays the same for stuff like equpment changes or int buffs dropping)?