David,
Just to let you know, I´m facing the same problem.
But I can´t say it that happened after the power cycle, because my stack is brand new.
Weird is the fact that I have replaced the switches of the whole building and only the 10th floor is having this issue.
Note: They are all Cisco Catalyst 2960 with the IOS version 15.0(1)SE2 - image C2960S-UNIVERSALK9-M
Regards Kleber