I have the same problem. Refer to the image I uploaded.
Only solution is to reboot the phone, it would be back to normal. But after a period of usage, it would appear like this again. I can't capture any logs, because I am not sure how and when exactly the phone would behave this way.
---------- Post added at 10:11 AM ---------- Previous post was at 10:09 AM ----------
I follow the instructions from this link:
[ROM][5.1.1][Official] CyanogenMod 12.1 for OPPO R7 Plus
This link is from Oppo Community Forum.