This was reported by another person last year, and I commented recently there too after I noticed the same exact thing you are reporting.

Here is the link to the existing open issue about this, where there has been some discussion already: https://seeclickfix.com/issues/14735717

The city knows this is an issue, but there is a problem/limitation with the video detector (camera) affecting the operation of the traffic signal due to shadows from the buildings. This means they have to manually adjust timings to ensure the lights don’t miss/skip anyone waiting because they are not detected due to shadows in the camera.

Unfortunately, there is no funding for an upgrade to the system, or for relocating it to correct the problem.

I’d recommend contacting your alderman and requesting they provide funding for necessary repairs such as this.

Here is information on the current alderman and how to contact: https://www.manchesternh.gov/Government/Mayor-and-Aldermen