I cleaned the ABS sensors in front about a month ago and haven't had the problem show up again.

However, the problem only existed for me on downhills and when it was raining and I haven't had too many of those downhills here in Fl.

The ABS sensors were quite dirty when I cleaned them, fairly simple to do.

I'm having the brake pedal switch changed tomorrow as a matter of fact. I told the guys at the shop where the car is what the error was and I hope they test the switch before they change it to see if that is the issue.

Once I cleaned the ABS sensors the light started coming on more sporadically, whether or not I was depressing the pedal which is very weird.

If you want, once they replace the sensor, I'll let you know if it pops back up again.

I see in your post that your shuddering happens when you brake. Mines would happen regardless of whether I was breaking or not. If you've completely ruled out that your rotors aren't a bit warped then your issue may be similar to mines.
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-Hector