Deposit XRP to mixin. Must be more than 20 XRP ( xrp tech sys compulsory ). Less than that amount. Lose. Become zombie.

Take out / withdraw from mixin to external network. Reserve 20 XRP ( dead , unable to wd out of mixin ), this is XRP tech sys. Not mixin issue.

The best thing is, we still can use our 20 XRP reserve to send between mixin network user. So, meaning our 20 XRP is still usable. That is the great of mixin. At official wallet. Our 20 XRP is totally dead forever.