Windows 10?i use the g27 as well and use paddles to shift (even in the renault alpine, shame on me) and the shifter pushed from neutral into 3rd gear for handbraking. works way better than a button for me, even without the rubber thingy.
On another note: at one point or another Dirt has renumbered my buttons (except for paddles and the top two buttons on the wheel, i.e. #05 - #08). My #017 button, which you need a lot e.g. to install presaved sets, is now 6th gear on my h-shifter, lol.
Check your profiler, has it changed to the basic wheel?