I've upgraded a customers controller a while ago from 09.21.04.0007 to 09.21.11.0004 and after that 802.1X auth wasn't working.
We've loaded the rescue image as there was not enough time to troubleshoot the issue.
Last week we've tried again this time we went to v10.11 and had the same issue.
After some troublshooting I've changed the shared secret to 12345678 just to make sure that there was no issue with the very strong key that we've used and it was working.
Today I was able to find the "problem" character - if § is used it doesn't work.
I assume it's a supported character as the controller doesn't show any error message if I save the key.
Customer used Windows NPS and I've used my NAC to test it so it looks like a problem on the controller.