A cashu mint can create sats without locking actual Bitcoin (Fake Wallet https://github.com/cashubtc/nutshell/blob/f32099bce7ecca54338ebc1a551883fbdb883af2/cashu/lightning/fake.py#L31). So the zaps you receive may or may not be real, i.e. convertible to Lightning sats. So you should either zap those sats onwards, or withdraw to a real wallet asap (claim from the mint). 

It this thing takes on and there will be lots and lots of such (potentially fake) sats on Nostr, this will inflate Bitcoin supply and damage it's reputation when many sats turn out unclaimable. 

TLDR I hate this shitcoinery.