Let me try a bit more. I successfully zapped you from amethyst.
Sending and receiving zaps in amethyst is independent. You can have two different wallets for sending and receiving.
Amethyst doesn't have a built in wallet. It uses external wallets to send and receive.
So when you say "received" or "sent" in amethyst, actually the external wallets are responsible for it.
All wallets can have intermittent issues. So a certain amethyst setup may work most of the time but occasionally fail because the sending wallet or the receiving wallet have a temporary issue.
Such as network issues, server issues, liquidity issues, routing issues etc.
What do you mean with "URLs in Amethyst"? Do you have an example of the error?