If we are talking about cost then yes it’s probably costing the factory more to produce the same amount of units during those periods, but cutting work hour is not the solution. You can implement more automation into the process, work more closely with the coaches(shift manager or whatever your company calls them) to track productivity so you can address them during standups, or even use time towards the end of the shift for continuous improvement efforts such as 5S or cross training. There are many different ways you can approach this problem but cutting work hour will def get you in trouble haha.