It takes time to move bags through an airport. Check in late or be on a connecting flight that arrives late and there may not be enough time to move the bag through the systems.
Interestingly, it can also work the other way; arrive too early and the bag disappears into the system to be stored temporarily and then forgotten.
I can’t say for sure, but I think the main reason for this is that the luggage space is being sold off to import products into Nicaragua. And once some luggage is held back, the backlog just gets worse and worse, and then it just keeps being held up. About half the time, I have had my bags not come in, and had to wait up to 4 days for them to come in.
Advice for checked bags is that you should always put at least one business card inside the case – that way, the airline can track you down and give you the bag back.