Error: [MobX] Cannot apply '@action' to 'ComplexType.prototype.create'

Error: [MobX] Cannot apply '@action' to 'ComplexType.prototype.create':
The field is already decorated with '@action'.
Re-decorating fields is not allowed.
Use '@override' decorator for methods overriden by subclass.

把mobx-state-tree升级到5.0.1试试

"mobx-state-tree": "^5.0.1",