ZFS – zpool replace never finishes

I have a 5 x 3TB raidz1 array on a ubuntu 14.04.1 server. Last month, one of the drives died (audible clicking). I was able to replace the drive with zpool replace RAID <dead drive> <new drive>. That finished without issue and the pool was online and healthy again. Then another drive died. I attempted the same thing, but the pool is stuck in the following status

# zpool status
  pool: RAID
 state: DEGRADED
status: One or more devices has experienced an error resulting in data
        corruption.  Applications may be affected.
action: Restore the file in question if possible.  Otherwise restore the
        entire pool from backup.
   see: http://zfsonlinux.org/msg/ZFS-8000-8A
  scan: resilvered 29.1G in 6h3m with 1028 errors on Mon Jan  5 05:35:35 2015
config:

NAME                                   STATE     READ WRITE CKSUM
RAID                                   DEGRADED     0     0 1.00K
  raidz1-0                             DEGRADED     0     0 2.01K
    ata-ST3000DM001-9YN166_Z1F15FAV    ONLINE       0     0     0
    ata-ST3000DM001-9YN166_Z1F15FCJ    ONLINE       0     0     0
    replacing-2                        DEGRADED     0     0     4
      17164957131155215254             UNAVAIL      0     0     0  was /dev/disk/by-id/ata-ST3000DM001-9YN166_Z1F15TBH-part1
      ata-ST3000DM001-1ER166_W500JFME  ONLINE       0     0     0
    ata-ST3000DM001-1ER166_Z500765Z    ONLINE       0     0     3
    ata-ST3000DM001-1CH166_W1F1M2C6    ONLINE       0     0     0

errors: 1028 data errors, use '-v' for a list

The good news is the data is non-essential. I am not worried about the errors (the files are videos and still play fine). I have tried the following actions to remedy this, as suggested by other questions and forums.

# zpool offline RAID ata-ST3000DM001-9YN166_Z1F15TBH
cannot offline ata-ST3000DM001-9YN166_Z1F15TBH: no valid replicas

# zpool offline RAID 17164957131155215254
cannot offline 17164957131155215254: no valid replicas

# zpool detach RAID ata-ST3000DM001-9YN166_Z1F15TBH
cannot detach ata-ST3000DM001-9YN166_Z1F15TBH: no valid replicas

# zpool detach RAID 17164957131155215254
cannot detach 17164957131155215254: no valid replicas

I have also run a zpool clear RAID and zpool scrub which triggered resilvers but left the pool in the same status as above. I then tried to remove the new disk, but oddly got the same no valid replicas error.

# zpool offline RAID ata-ST3000DM001-1ER166_W500JFME
cannot offline ata-ST3000DM001-1ER166_W500JFME: no valid replicas

I am at a loss for how to proceed. It appears that the replace was successful, but zfs won't let go of the original disk.

# dkms status -v
spl, 0.6.3, 3.13.0-43-generic, x86_64: installed
zfs, 0.6.3, 3.13.0-43-generic, x86_64: installed

Update: I removed the zpool cache at /etc/zfs/zpool.cache and rebooted. Resilvering again, will report back.

Update 2: Still in the same status as above. If there is no way to finish the replace, is there any way to rebuild the pool without loosing any data?

Update 3: Here is the most recent status:

# zpool status
  pool: RAID
 state: DEGRADED
status: One or more devices has experienced an error resulting in data
        corruption.  Applications may be affected.
action: Restore the file in question if possible.  Otherwise restore the
        entire pool from backup.
   see: http://zfsonlinux.org/msg/ZFS-8000-8A
  scan: resilvered 29.1G in 6h1m with 1028 errors on Wed Jan  7 03:49:13 2015
config:

    NAME                                   STATE     READ WRITE CKSUM
    RAID                                   DEGRADED     0     0 1.00K
      raidz1-0                             DEGRADED     0     0 2.01K
        ata-ST3000DM001-9YN166_Z1F15FAV    ONLINE       0     0     0
        ata-ST3000DM001-9YN166_Z1F15FCJ    ONLINE       0     0     1
        replacing-2                        DEGRADED     0     0     0
          17164957131155215254             UNAVAIL      0     0     0  was /dev/disk/by-id/ata-ST3000DM001-9YN166_Z1F15TBH-part1
          ata-ST3000DM001-1ER166_W500JFME  ONLINE       0     0     0
        ata-ST3000DM001-1ER166_Z500765Z    ONLINE       0     0     0
        ata-ST3000DM001-1CH166_W1F1M2C6    ONLINE       0     0     0

errors: 1028 data errors, use '-v' for a list

The smartctl data for all 5 drives is here.