In the current version of forge, TickEvent.PlayerTickEvent happens twice for each player tick: one at the start of the tick, and one at the end. Mod developers are supposed to use if (event.phase == Phase.START) / if (event.phase == Phase.END) to distinguish between those two.

Since TickHandler.playerTick doesn't do the check, several bonuses are applied twice each tick. For example, a single level of Furnace Finesse (with default multipliers) causes furnaces to work five times as fast, instead of three times as fast.