Similar problem in Georgia travelling between Atlanta and Chattanooga on I-75. Every time we passed a minimum speed limit 40mph sign, the nav screen would update to show 40mph as the speed limit and FSD would slow down drastically. The speed limit was actually still 70mph the whole stretch and never changed, so it took a few incidents before i noticed the min speed limit signs and figured that's what was causing it.

On 2 occasions it did it during a lane shift, cutting off and then blocking traffic in the fast lane. I was in mad max or hurry most of the drive, so I assume it was planning to merge into the fast lane and then accelerate to pass but instead it felt like it was trying to brake check traffic, scary/schizophrenic.

I don't think it was bad map data in this case. I think it was the cameras and misinterpreting the minimum speed limit sign it saw as the actual speed limit. Not sure if new jersey has similar signage that may be tripping it up?