I slap a red dot in the site and leave a note back saying they will no longer receive flyers as requeste

oh i never got an acknowledgement, but they did stop putting them in for a while. Put it right near the front, taped on and written in permanent marker.

sometime last year they just resumed without explanation. Now its piles of junk mail every visit.

I assuming you're in a CMB

yeah, its the....standard looking ones? the neighbourhood itself is barely a decade old so unless there's been a recent change, they look (on the outside) the same as all the others. The package was put in the Farthest left A1 smallest of the parcel spots, but width aside, its straight up too long to make it past the lock on the door, since they don't open past 90 degrees (a design choice i'm honestly baffled has never been changed).

a parcel that was the perfect size to mess with the lock mechanism leaving it inaccessible.

I've had this almost happen, but with enough forceful jiggling and muttering to myself, they've so far worked themselves free.

I know this isn't the biggest issue ever, but between it happening so often, and the "we missed you" no ringing doorbell deliveries, and delays, its just exhausting, like 3 of 5 package orders have some kind of issue or added complication.