An error that may be surprisingly addictive. Or rather, it is already stuck.
http://dropwne.jugem.jp/?eid=211
It seems to occur often due to errors in SQL statements, but the error I'm seeing now is not using SQL statements.
Then, I found a suspicious place.
It was just a spelling mistake!
My reference method in $this? showed that Response was Repsponse. Fixed and successfully resolved.
If you're having trouble, you might want to look at yourself with var_dump($this).