I have been fighting with this since morning with no solution yet, I also tried to remove the iOS platform and added again in case I messed up something but I had no luck.
This happen in the iPhone 5 iOS 8.1 simulator for me.
After reading several posts in the web, including SO and other frameworks this is present in both the simulator and real device, check here: https://github.com/emberjs/ember.js/issues/5606 . Although that is for ember I have read similar reports on angular applications.
It is not the same time I read about removing the “use strict” mode on the angular files. I haven´t tried yet.
Also check here at this bug report: http://trackjs.com/blog/tracked-attempted-assign-readonly-property-ios-8-typeerror/
I will try to apply some of the above changes in order to see if that solve the problem and do not welcome other problems on board.
Please let us know any update about this matter.