Receiving (on OS X and iOS) notifications in Calendar about Reminders

Question

I've had this problem for as long as reminder lists were able to be shared.
I've setup a shared Reminder list with my wife. It works fine.
The problem is, every so often (and I stress, "so often" - not all the time, which is partly why I can't figure out a solution) I will get notified that "XX items were updated/changed by Emily on Shopping list". There are two problems with this:
The alert actually comes from the Calendar app. I know these two apps used to be intertwined but I've never used them when this was the case. Hence, I can never figure out why this is actually happening, as they are now, as far as I can tell, two separate apps.
The alert is delayed and does not align with an actual update to the list. When the alert comes through, my wife has not in fact updated or changed anything. It's arbitrary - the number of items is usually even more the (current) number of items on the list. I open Reminders quite often (loading new or completed items) so it can't be happening whenever new items are loaded. Furthermore, as I said above, it is not all the time. I actually can't tell you how often it is, but it far less than the app is used (by both of us). We update it nearly daily and this alert only comes through (on either iOS or OS X) maybe once every few weeks, or monthly. Hence why I've waited so long to find the root cause.
It's more of a curiosity thing at this point, as I'm so used to dismissing the notification now. Hope someone out there has an idea of what's going on.
I'm thinking I'll setup a new reminders list and share that with my wife and see if the same issue happens. However, as the issue only comes up every few weeks to a month, I won't really know if it's fixed until a few months have passed. But, I'll come back here in a few months and let people know one way or the other.
PS: I apologise if there's another thread addressing this - searching for "notifications in calendar about reminders" is not helpful at all and I really had no idea how to find such a thread, if it exists.

Answer 1

since morning today i have been running the iphone 4 with safari icloud sync turned off. i also left bookmarks sync from itunes off. i unplugged the charger at 100% charge at excatly 10 am. i am on 86% at the moment and its 5.30 pm. however i had to plug in the phone to my macbook for 3g internet access at about 91% which got it charged back to 100%. that was for about 30 minutes. so i guess i would had been at around 75% if i hadn't done that.
so i think people are right about the bookmark causing battery drain thing.
tomorrow i am gonna try with the phone rebooted and charger to 100%, with no location service running in the background, just when the app is running, and with all bookmarks deleted from my iphone. if i have to use 3g off my iphone i would use wifi personal hotspot. usually all this use... a few calls, some internet access, whatsapp, maybe a few pictures, and music for say about 2 hours should still leave me 40-50% battery by night, after 16 hours of use. if that goes well, i might have saved my self restoring the iphone to new.
as for the mac, i figured out a way to use timemachine for a smaller hdd. i will simply 'move' those files i dont want to keep on my ssd anyway, to an external hdd. like podcasts, videos and movies. then take a TM backup when the used space is under 120 gb. and then restore that to the SSD. should work, hopefully.
Neerav