Wiko Rainbow - repair / fix invalid IMEI error / bug - super easy
Did you also ran in that annoying "INVALID IMEI" thing while flashing? Okay. There are a lot of guides out there. And all of them (more or less) bring back the IMEI in some way. But for all what I know, it's gone anyway, the next time you install an OS. So why bothering to install Recoveries and such in the first place? This way shows you how to "fix the imei" without. All on your own risk.