There is stock but it's out of stock

Sometimes items become out of stock even though they are in stock.
This happens with both custom items and regular vanilla items.
The first one will be available for purchase, but after that it will appear to be out of stock and will no longer be available for purchase.
Do you have any idea what the cause is or what the solution might be?

When I relist the item, there doesn't seem to be any particular problem.
It can be purchased as normal, but this issue has been occurring at some point, whether it was the first time or at some other time.
I thought about avoiding this by registering the same item multiple times, but multiple items end up being out of stock at the same time (even though they are in stock).

The server is restarted twice a day, and I just restarted it, but no problems occurred.
I think this happens when you register for the first time after the wipe, but I'm not sure of the timing.