Fail to install CM13 on Oppo Find 7a
I recently went through this on my Find 7 so hopefully I can help.  Here's what I've found to be foolproof.


Download the latest ColorOS software and copy it to the device's SD card (either internal or external is fine if your partitions are not unified; external otherwise).  You can also save CM13 there at this point.
Download and flash the latest stock recovery.


Extract that zip file to your current working directory on your PC, put the device into Fastboot mode (hold Power + Volume Up), and run:

fastboot flash recovery ./find7_recovery_4_4.img


Hold Power + Volume Down, releasing the former when the device vibrates and the latter after the recovery screen comes up, to boot the device straight into that recovery.
From recovery, flash ColorOS 2.1.5i and then select the option to reboot; let the device do so.
Download and flash the latest TWRP 3.x recovery: https://dl.twrp.me/find7/


Similar to (2), different filename.

Repeat (3), and you should be in TWRP and can flash CyanogenMod!