I noticed this as well. On Sunday, I actually made a left on red. Yesterday, I sat longer, and it does in fact change, but it took about 4 minutes. The sensor must be malfunctioning.

We also made a left on red this past Sunday. I noticed that it does change immediately when a vehicle approaches from the east side.

It appears to be fixed, however it now changes from a significant distance away from the light so you have to speed up in order to catch the green or it will go to red before you get there.

Issue seems to be resolved.