OP, I can't see behind what you've told us. But let's say that often we see threads from private delivery drivers (Evri, Amazon Prime etc.) who have fallen foul of limited parking places, including unrestricted yellow lines, while delivering parcels, sometimes multiple drops in an area.
But back to your situation, IMO your only argument so far would be that you were delivering whatever to wherever and that you thought that unloading/delivering was permitted in these bays.