I'm having some good luck (so far) with the following registers. I got desperate and started randomly changing register values with a 'what if' ideology, and now I'm not seeing the spike.
It's probably due to some filter change, but I'll keep slowly changing my registers back to the original to see what it was that's changed everything.
Give these a try and let me know how you get on:
GYRCTRLREG1, 0b01001111
GYRCTRLREG2, 0b00011001
GYRCTRLREG3, 0b00000000
GYRCTRLREG4, 0b10110000
GYRCTRLREG5, 0b00111111