Ok, I've sent you a link for a recovery image.
First, you determine which slot you are on using ADB in the normal system. Follow these instructions, but stop if doesn't look like this. The ... is where it reboots.
Code:
C:\>adb shell
$ getprop | grep suffix
[ro.boot.slot_suffix]: [_a] -- or it might say _b
$ adb reboot edl
...
C:\>edl /lwhatever
C:\>edl /w /precovery_a rec.img -- or you might need to say _b
C:\>edl /z
...
C:\>adb shell
$ reboot recovery
...
-- You should see it boot to a white screen --
C:\>adb shell
# start ttyscreen
-- Do you see text on the screen or at least wiggly lines? --
# reboot
...
Good luck.