Scheduled membership reminders sends multiple times

I've added 2 scheduled reminders for memberships:

• 1 month before Membership End Date

• 1 week before Membership End Date

Now the first one fires (and stores an "activity" record for that person), so when I get the payment, I extend the membership (by a year in my case).
However, the second reminder is still being send and without logging an "activity" for that person (but I know they received the second reminder because I frequently get complains about that).