Easy Repair "OPPO Wipe Failed Syndrome" without change the EMMC using UFIBOX.
This is common problem on most OPPO Mediatek Devices with SKHinyx eMCP inside.
Like Oppo R815, R821, R827, R831, R831K, R1001, R2001, etc.
We use Direct ISP to Repartition The EMMC,
Solder only 4 wire : CMD, CLK, DAT0 & GND, use Usb Data Cable for VCC & VCCQ
Factory reset emmc, do repartitioning, and write preloader
Flash devices with stock rom using any mediatek flasher you have
And You're DONE.
Latest UFI Android Toolbox already support Flashing and Repair Imei of Mediatek Devices