In the revert/force flash thread referenced in the first post, it gives you the substitutions for Force Flash VC in the reference section. Just follow the Force Flash V9 instructions and substitute what is mentioned in the reference section.
Though the chance for some type of failure is not high, I always suggest you make a backup before flashing.
First was there might be different sized recovery partitions on different models. However your recovery partition is the same size as other phones.
The second explanation is that the recovery.img is a full backup of the entire mtd2 partition, even the portions that are empty. So the reason you are probably seeing the error is you actually do have a bad block (memory) in your recovery partition and the reason you see it flashing the v9 recovery.img is because it is exercising the entire range of memory in your recovery partition, whereas the other recoveries are only as big as the recovery needs, and/or they are smaller in general, so they are avoiding the bad block(s).
You can try an updated flash_image to see if that helps (I didn't look at the source to see if it handles stuff differently, so I'm not saying it will behave differently)
You can also just try rebooting to recovery and seeing if the V9 recovery comes up. There is a chance the important parts of the recovery.img were already written before hitting the bad block, so even though there is a write error, it isn't relevant. Do not use "adb reboot recovery" as I believe that will write stuff to the misc partition which might get you into a loop if your recovery is bad. I think using Power Down / Home + Vol- + Power will be ok.
I can also post a minimal recovery.img with the empty blocks removed to see if that avoids the bad blocks. Let me know if that is something you want to try.
You could also just run the V8->V9 update.zip. It should create the recovery partition by patching the boot partition. It should work in theory, but again, I haven't traced the exact mechanisms it is using to handle the various reboots and writing of flash memory, so couldn't tell you for sure it wouldn't get you into a boot loop.
There might be a way to format the recovery partition and lock out the bad block, but I don't know enough about the MTD tools to advise you on that.
I'm just warning you in advance about potential problems. I'm not saying any of these are likely.
So IMO the problem is with the flash memory on your device.
So let me get this straight: my phone is vd updated from lg tool and rooted so to unroot I just have to manually flash the v9 stock recovery, then use the lg updater tool to flash vd again and then follow directions 3-4?
I'm trying to manually flash v9 stock recovery and I tried it on terminal and it says cant read flash image and when I try it using adb shell its saying it doesn't have a path and adb is not recogninzed as an internal or external command? I have this phone on e bay and I need to unroot it today
can't you just force flash back to zvc? when I done it it gave me complete stock rom and recovery. be easier I think if you want to go back to stock.
1) Force flash often (but not always) leaves your existing recovery in place
2) Force flash doesn't touch your /data so your apps and personal info are still there
3) Force flash doesn't touch your NVRAM so your Sprint login and phone # are still there
Certainly you can skip steps if they aren't important for your needs.
Simplified UNROOT and return to STOCK procedure for users already rooted
(these instructions are written at a summary level so you need to know some basic terminology/techniques):
1) Manually flash the stock V9 recovery (Reference Section below). Skip if you already have stock recovery.
2) Force Flash V9 (or V8, VC, VD in KP500 reference section, use VD if you have new LCD) - see KP500 thread - skip step (u), ie step (3) in the summary
3) Power down phone and boot into recovery (Home + Vol- + Power)
4) Choose "wipe data/factory reset" if you want everything factory fresh or "wipe cache" if you want to keep your data and run stock
NOTE: If you want to scrub even your Sprint data login information and phone # from NVRAM, for example if you were to transfer/sell the phone to someone else, perform a ##786# reset from the dialer in Android (you'll need your MSL/SPC/Service Code - ask Sprint or use CDMA WS)
Manually flashing stock V9 Recovery image (requires root) UNZIPflash_image and stock V9 to /sdcard