ouright, in your patch you're using the Enum2String (Enumerations Explicit) version which allows you to explicitly specify an enum (via inspektor) which propagates upstream and confuses the IOBox that in this case already has another enum connected.
use the Enum2String (Enumerations) instead in this case and you'll see it just work as expected. note though that you cannot simply replace the node in your patch as the IOBox is already confused. also create a new IOBox!
the explicit version is rather to be used if you have an IOBox only connected to an Enum2String node as it then allows you to specify the enum you're interested in.