Blinding powder triggered the cd (while not a ability itself) of Signet of agility.
Happened in wvw ONLY, after the balance patch. Blinding powder was set to 7 and Signet of agility was set to 8.
Happened every time, also after client restart.
Workaround:
Swap the two abilities (Signet of agility to 7 and Blinding powder to 8 ). Bug is gone, even if you swap it back to the initial binds.