The Self:Initialize state of the DEV actor template does not send replies anywhere and is handled before any Registrations are received, thus any error in this message are not reported to calling code. The error dialog is also suppressed if the actor is "launched" by a caller. So errors in initialization are lost.
Proposal: have an optional input on "Launch" that accepts registration messages, which will be applied to the Observer Register before "Self:Initialize". Could have a "Launch and register for errors" method as well.