HELP: Pin Code haas been changed automaticaly

Hi,

Yesterday I entered my Pin to unlock my phone but it was not accepted. I've tried it 4 times and after that my phone booted and switcht back to factory settings because of the Exchange security policy.
I was 1000% sure I've entered the pin code correctly. I'm typing the code 50 times a day and for 3 years now.

Set up the phone again and configured eveything and today I had the same issue again..

Does anyone has the same issue?
Does anyone what it can be?
Could it be caused by Exchange? This is the only app who has access to the system.??

I'm using the A.I Type keyboard interface.

My Phone details:
HTC One S
Android 4.1.1
HTC Sence 4+
Softwarenumber: 3.16.401.9


Please let me know if you have an idea
Thanks in advance!