The answer is trivial and hasn't anything to do with retain counters...
I oversaw that it isn't allowed to name variables/properties starting with new
with ARC enabled. This obviously resulted in an over release thus generating the error...
From Apple documentation: https://developer.apple.com/library/ios/releasenotes/objectivec/rn-transitioningtoarc/introduction/introduction.html
To allow interoperation with manual retain-release code, ARC imposes a constraint on method naming:
You cannot give an accessor a name that begins with new. This in turn means that you can’t, for example, declare a property whose name begins with new unless you specify a different getter