I have the Q88+ and the only issue on my device is the non-function of the left speaker.
Neo-Nemesis can confirm that.
But the speaker are so lousy... better use good Headphones.
All the buttons and sticks works.
My Handhelds: PS Vita, PSP (1000), New 3DS, NDS lite, GBA SP, GB Micro,
LCL Pi-Boy 3A+, GPD XD (Old), PowKiddy X18, RG350, PlayGo, GKD350H.
Favorite: Odroid Go Advance