Of course everyone should take their break. And go to the bathroom whenever necessary.
But sometimes things are more complicated than you think.
Show me in the New England Supplement where it says a part-timer is entitled to a break.
Show me in The Law where a part-timer working, say, four hours plus or minus, is entitled to a break.
Maybe there's a "Past Practice" of taking a break, but that's not as secure as actual legal or Union Contract language.
There's also the complication that typically part-timers don't control the conveyor belt system. If you leave your workstation for a break on your own authority, you may be seen as abandoning your job, or failing to work as instructed. Especially if the packages keep flowing in your absence. Either you will be burried when you return, or the workers downstream will be in your absence.
The Union should step in and insure the belts are stopped so a break can be taken without appearing to be insubordinate.