D&C needed after planned c section

I posted the other day about clotting and bleeding and went to the ob yesterday for an ultrasound and discovered remnants of my placenta are still in my uterus.

The doctor said this is very rare and a d&c is needed. I am still confused how this is even possible with a c section - has anyone else had this happen? Surgery is scheduled for tomorrow to remove.

Is this malpractice? My ob was not my OB the entire pregnancy, unfortunately my original doc moved and I was moved to her towards the end of my pregnancy. This is the head doc at the practice and has won multiple awards for being top doc in my area. She mentioned when the uterus contracts sometimes the placenta can contract with it and go up near the fallopian tubes which is how remnants were left behind but the more I think about it the more I don’t understand. I did also donate my placenta during birth - never knew that was a thing but apparently it’s used to help make skin grafts.

Has this happened to you?

C section was 12/22

Red blood for about 4 weeks

5 weeks black blood up until 2/12. Bled through pants and passed a quarter size clot bright red. Black blood from 2/12-2/15.

2/15 in evening bled through pants again bright red. Woke up in the middle of the night with stomach and back pain, passed a larger clot. Red blood from 2/15 to current. Ultrasound 2/18.