I ran through some more kernels and then when I re-tested 4.2.0-040200rc1-generic it did not work. So I re-tested some kernels doing five runs each time. (B=Broken, W=Works)
3.19.0-50-generic - WWWWW 4.2.0-040200rc1-generic - WBBBW 4.2.0-040200rc2-generic - BBBWW (201507151846) 4.4.0-6-generic - BBBBW
So it appears it has gone from working reliably in 3.19 to being unreliable in 4.x, failing in the order of 20-40% of each boot.
Note I blacklisted the hid-multitouch module so for these tests I was manually modprobing it after boot. Also 4.4 tends to boot slower than 4.2.
I ran through some more kernels and then when I re-tested 4.2.0-040200rc1 -generic it did not work. So I re-tested some kernels doing five runs each time. (B=Broken, W=Works)
3.19.0-50-generic - WWWWW -generic - WBBBW -generic - BBBWW (201507151846)
4.2.0-040200rc1
4.2.0-040200rc2
4.4.0-6-generic - BBBBW
So it appears it has gone from working reliably in 3.19 to being unreliable in 4.x, failing in the order of 20-40% of each boot.
Note I blacklisted the hid-multitouch module so for these tests I was manually modprobing it after boot. Also 4.4 tends to boot slower than 4.2.