I work in a manufacturing company where I am required to basically monitor machinery and process paperwork (not giving too much detail to keep anonymous).
It is generally expected people be on the floor around their machinery in case anything goes wrong and the machines require manual input here and there.
I work 8 hour shifts a day with 4 hours total travel to and from, making me out of home for 12 hours. Usually I will take a bathroom break (bowel movement) as I'm there for majority of the day, I find the walking around a lot I do on the floor will also stimulate this. I basically cannot help when I have to go. I try not to take more than 10 minutes when I do go, but it can depend.
I've had two supervisors sit me down and ask about being absent from the floor, saying they were running around everywhere trying to find me (melodramatic and unnecessary about something that was not at all urgent and could wait). I usually tell whoever is around I'm going to the bathroom but if there isn't I'm not going to wait around. I've also had them say this about taking my lunch break, that I couldn't be found anywhere despite taking my lunch break same time everyday. I find it amazing they are unable to deduce this.
I find it ridiculous they will pull me up on this, there are many people in the lab that will disappear for long periods of time and get away with it. I've known one colleague go to the shopping mall on their lunch break for over an hour and get away with it. The supervisors themselves often disappear, sometimes for an hour without telling anyone where they are.
What is the best way to handle this because so far it's coming across as petty micromanagement and a double standard. I find the management very hard to take seriously.