There are 3 borders in the same area. All in Southern Ontario but all much different.
Rainbow Bridge - Best place to hand in waivers in Ontario, in the town of Niagara Falls. Easy to find. Great hours. NO TRUCKS ALLOWED. No waiting. From October to May they take waivers on SUNDAYS from 5pm - 9pm. That is when most of my clients go (during those months) and I never get a single complaint. Even though I forward my phones, I NEVER get a problem on a Sunday, just the occasional (on my way home, it was exactly as you said)
Queenston/Lewiston off the 405 highway, near town of Queenston. Decent hours BUT no weekends ever, and they get busy with truck traffic. Sometimes you go right in, sometimes you wait. No Sundays.
Peace Bridge, near Fort Erie /Buffalo - hours are just ok (Monday-Thursday 5pm-9pm) lots of truck traffic, too busy. Avoid.
This thread is about handing in your waiver. This is DIFFERENT from being denied entry. Of course when they deny you entry its a bad experience. Of course if your caught at the Rainbow Bridge its going to suck. But when you are handing in your waiver you are telling them you are not trying to cross and are there to hand in waivers. They are very pleasant 90% of the time under THAT circumstance.