We have a direct channel with coinos with plenty of liquidity. That channel might've gone offline temporarily. Nor you or I can control the availability of third party custodians, so things like that will happen occasionally.

Regardless, you're more likely to receive large zaps as sats than small ones, because we pay the network fee for you, but we will only pay 3% of the zap amount. If the zap is small, the fees are more likely to exceed 3%; e.g. a 10 sat zap with a fee of 1 sat, or 10%, will be too high. In the future, we will allow you to elect to pay the network fees yourself, but in the meantime this is how it works.