Grumpy_Mike:
Can you explain why this would make it worse?
Because when the switch has been triggered it is only being pulled down with 1K5 which is not as hard as a direct pull to ground therefore making it more prone to interference.
What happened when you tried the fail safe option of having the switch normally connect to ground?
The way I see it you have a grounding problem.
Good point. Do you have any suggestions for how I should filter out the noise?