1 year post-op. Why are my teeth moving even after wearing nightly Invisalign retainers?

Hello Chila,
Yes, your passive aligners are not able prevent teeth movement over time. I'd suggest you schedule with a Board-Certified Orthodontist who can provide you comprehensive care to address your bite, or teeth movement.  Each patient is unique so you'll want to see a doctor in-person for an evaluation.  
Best regards,

Dr. Vickie Greenberg

Chila:
This is a difficult question to answer here, and I would recommend seeing the dentist who performed your Invisalign treatment.  It's possible that the aligners have distorted and are now putting pressure on your teeth.  But more likely, there is something about your bite which is encouraging teeth movement.  It's also very possible that you are clenching or grinding your teeth, especially at night.
Passive aligners aren't really designed for use as retainers -- so I would ask your dentist about getting retainers made.
Good luck!Kevin Fitzpatrick, DDS, MS