Hi Zelig,
Sorry for that and I'm working on it these days.

So far, unfortunately, this bug is hard to be reproduced on my phone, actually i have been trying to reproduce it for over hundreds of times...
here is some conditions i have tried:
1\ Deny blacklist mode with 200 items(including wild char patterns)
2\ open many apps to make system in a low-memory condition

so I guess the bug is depend on the phone's environment(CPU usage or memory usage). and i'm not a heavy users of N9...

So if possible, would you mind to give some more detail information to fix it? such as:

1\ which call block mode or Easy Profile is chosen?
2\ How many items in blacklist/whitelist?
3\ the bug can be reproduce 100% on your phone?
4\ the memory usage
5\ opening app list when the bug occurs

you can PM me the deail...

Thank you so much!