All petitions go through some degree of post interview administrative processing. If your name is common, if you have a lot of address changes, if you've been to Timbuktu and back, basically if the wind blew whatever way, that can impact AP.
As I'm sure you've worked out, Montreal is a SLOOOOOW consulate. A week to 10 days is pretty standard for standard AP clearance.
Also, don't panic if your CEAC status changes to "refused" before "issued". That's normal, too.