When transport ship has 14 bombards and 1 scout I was unable to load another bombard into the transport ship.
Putting the 15 bombards in first before loading the scout works fine alowing the same number of units to be loaded into the ship.
Selecting the bombards after clicking on the transport and right clicking the shore does not allow the bombards only to be unloaded.
Selecting the scout in the transport ship and unloading only the scout onto the shore works fine.
Only way to unload the bombards was to ensure all units including ship were selected and using the unload garrison button/hotkey in the UI
Should be able to unload bombards only by selecting them from the transport ship and right clicking the shore just like the scout. If you have multiple different types of units in 1 transport including bombards and mangonels and some of one type and reload them it seem to trigger something that prevents you from then unloading only type of of unit by selecting them and right clicking the shore.
See below video for issues after unloading certain units types and reloading them causing ship to prevent you from unloading units individually.
Playing as English on blackforest with no other players in the game.