Welcome! This forum has a treasure trove of great info – Scouters helping Scouters! Just a heads up, though - all content, information, and opinions shared on this forum are those of the author, not the BSA.
I have a scout who is also a sea scout. Every time I enter a MB requirement, it defaults back to his ship, so I have to click his name, troop, advancement, then mb again. I have to do this for every single MB requirement. His parents say it defaults to Ship for them, too. I have no position in the Ship, though.
I haven’t entered any rank advancement requirements for him recently because he is an Eagle Scout, so I am not sure if it happens there, too, or just merit badge requirements. It makes entering MB requirements for him very time consuming.
You can go to the Scout’s membership for your troop and set the default unit setting. This must be done on a browser by browser basis. This is to allow leaders of the ship to have a different default.
There was an issue that was fixed tonight that caused the behavior you explained, even if the default unit was set.
I found the place in his membership to set Scouts BSA as the default unit, set it, logged out of ScoutBook and back in, and it is still switching to Ship after I add a merit badge requirement. Is there anything else you know of for me to check?