While that sensor is typically pretty good about surfaces, it can be picky about pattern and color changes. You can try to increase the lift off distance to see if that helps. Different colors reflect light in different degrees of intensity. If you have the LOD set super low and the orange reflects less light, then the sensor won't get enough data to respond. At least that's how optical works from what I understand.
Also, that mouse works far better on a hard pad. Many...
I believe the FK1 clicks are lighter than my FK and AM. The shell is a bit larger, so the button leaves are longer. The AM-GS with Omrons feel better to push, but I'd be really surprised if they took measurably less pressure to actuate than the huanos.
You seem to have performed up to your expectations with the 1.1, so why not buy another off of amazon? I went searching for them a couple months ago and they were pretty easy to find in OEM packaging.
If you're wanting something a bit newer, then I'd look at the Final Mouse, or the EC1-A. They're about as close as I've come to the shape/feel/performance to the older MS mice.
1.) Zowie EC2-A: What an incredible mouse. The shape is one of my two all time favorites. The sensor is great. The size is right. The cord is great. The huano switches feel good in this body. Overall, it's a fantastic iteration of a mouse that would have made the list for me at any other time.
2.) Zowie AM-GS: My favorite fingertip mouse ever. I had to frankenmouse this unit to install the FK1 innards, but it just created a perfect shape and material for me.