Trouble with inventory type app

I created a Glide app last summer and it was working exactly as intended since October. In the last few days, it’s no longer working the same which is causing big problems for us. Our app is for Keg reservations and this is the information I need to keep current at all times:

  1. Current inventory - actual product on hand. We adjust this quantity manually when product is received. I have this on three tabs by keg size: 1/2 barrel, 1/4 barrel, 1/6 barrel.
  2. Reserved inventory - customers use app to reserve the keg they want to pick up. This is on one tab: Reservations
  3. Available inventory - a calculation of Current - Reserved triggered at the time Reservation is made.
  4. Picked up - Once keg is picked up, our staff hits a “picked up” button which reduced the “quantity reserved” by 1 leaving a 0 in that cell
  5. Back to Current inventory, we have been manually adjusting current inventory number at the end of the day by deleting the 0 in the reservations tab and manually changing Quantity on Hand number on the corresponding keg.

Previously, after a keg was picked up if we deleted the zero in the reservations tab, it would add that keg back to Available inventory. Now, it is adding that keg back to Available inventory upon pickup which makes it available for another person to reserve when it is not!

If there is a better way to track the numbers i need, I’m willing to make any recommended changes