Hi Peter, Thank you for your reply.
hard to figure out from afar. Do you have your code available on github?
Regarding 1): I don't know how this should be related to you memory violation issue.
Regarding 2): AFAIK your thread will have the priority that you give on initialization, no matter from where it is created.
I have tested the same scenario (thread creation with higher priority and with THREAD_CREATE_WOUT_YIELD) in /test/xtimer_msg project. All worked fine. So this could be a specific problem with my project or it could be connected with another threads running in this specific program.
It is not caused by insufficient stack size.