Strange Morphia Exception caused by Rythm

This very strange exception drives me crazy!

The exception pops up when I've updated a model class, and it won't go away unless I've restart my play app. Crazy!

Initially it looks like it's a problem of PlayMorphia, and I was thinking it is a PlayMorphia problem because I've just added an new feature allow processing @Converters annotation intelligently. I've tried to switch back to previous version and I found it's still there! And rewind to the version before previous version, it's even still there!

Finally I found it's caused by a recent updates to PlayRythm. Specifically the following code:

And the problem has gone when I changed it to 

So obviously I need to reconfigure the Rythm Engine in dev mode even when the engine has been configured and initialized during pre-compilation process.

This is very strange and I've still no idea on why it happens