I bought the magnetic titanium bolts (X6) two years ago.
I did mount the titanium bolts this winter and did my first ride with the titanium bolts in the beginning of the spring this year.
I noticed that the speedometer did only show about half the speed that I actually was going.
And yes all 6 bolts was wit the magnetic inlay.
I did remove the titanium bolts again and then I did use the OEM brake disc bolts again for a while.
Then I did try to investigeate what did cause the misreading. The result is that 3 of the Bolts have the magnetic inlay mounted in the titanium bolt so that the magnetic field that is in the end of the titanium bolt is a magnetic North and the other 3 bolts have the magnetic inlay mounted so it creates a magnetic South.
In that way the mix of magnetic North AND South is interfering the signal that should trig the Hall-sensor.
All in all I bought 3 new bolts with the same polarity as 3 of the bolts I already had.
So now I have 6 bolts with the same polarity - and it works now!!!!!
So all in all make sure that the magnetic polarization is identical for all 6 bolts if you are going to buy the titanium bolts.