I have just gone to look at my priorities list and they have all been duplicated!

This is the second time that this has happened.
The last time I just removed each duplicated priority, one at a time.
I think this is probably be the solution this time ... but how do I stop this happening in the future?
I only have one other computer linked in with my Logos account, and that is my mac, running A6.
Thanks.
[Edit] Not all of them have been duplicated. I was experimenting with some last night (offline - capping issues). These have not been duplicated.