A Booking Already Underway Now Outranks a Later Reservation

A booking that had already started could get stuck. If anyone reserved one of its items after it began, that reservation blocked the in-flight booking from ever handing the item out, and there was no way to resolve it from inside Shelf. The item's row still showed as Available, so the action was offered right up to the moment it failed with "Some assets are already booked or checked out elsewhere".

The priority now runs the sensible way round. A booking that is Ongoing or Overdue outranks a reservation created after it started, and can check out the items it is already holding.

Nothing happens quietly. Both bookings get a note on their activity timeline naming the other booking and the items involved, so the reservation's owner finds out straight away rather than at their own check-out. If a reservation loses an item, swap in a replacement before it starts, or shorten the booking that's holding it.

The rules that mattered before still hold: two reservations clashing still block each other, an item physically checked out on another in-flight booking still blocks, and an item in someone's custody still blocks. This applies to individually tracked items only, since pooled stock is counted rather than claimed.