[Shield Android TV General] Luxferro:
Here's the recovery.fstab from the stock recovery.img for the 500GB model:

# Android fstab file.
#<src> <mnt_point> <type> <mnt_flags> <fs_mgr_flags>
# The filesystem that contains the filesystem checker binary (typically /system) cannot
# specify MF_CHECK, and must come before any filesystems that do specify MF_CHECK
/dev/block/platform/tegra-sata.0/by-name/APP /system ext4 noatime,ro wait
/dev/block/platform/tegra-sata.0/by-name/CAC /cache ext4 noatime,nosuid,nodev,data=ordered,nodelalloc,barrier=1 wait
/dev/block/platform/tegra-sata.0/by-name/LNX /boot emmc defaults defaults
/dev/block/platform/tegra-sata.0/by-name/MSC /misc emmc defaults defaults
/dev/block/platform/tegra-sata.0/by-name/UDA /data ext4 noatime,nosuid,nodev,data=ordered,auto_da_alloc,discard,barrier=1 wait,check,encryptable=/dev/block/platform/tegra-sata.0/by-name/MDA
/dev/block/platform/tegra-sata.0/by-name/USP /staging emmc defaults defaults
/dev/block/platform/tegra-sata.0/by-name/MDA /metadata emmc defaults defaults
/dev/block/platform/tegra-sata.0/by-name/SOS /recovery emmc defaults defaults
# w/o built-in eMMC
/devices/platform/sdhci-tegra.0/mmc_host/mmc1 auto vfat defaults voldmanaged=sdcard1:auto
# with built-in eMMC
/devices/platform/sdhci-tegra.0/mmc_host/mmc2 auto vfat defaults voldmanaged=sdcard1:auto
/dev/block/platform/sdhci-tegra.0/by-num/p1 /sdcard vfat defaults recoveryonly
/dev/block/platform/tegra-sata.0/by-name/BMP /bmps emmc defaults recoveryonly

############### USB Drive Configuration ##############
# P1963-E00 IO board
## config#1
### usbdrive
/devices/platform/tegra-xhci/usb2/2-2/2-2.1/2-2.1:1.0 auto vfat defaults voldmanaged=usbdrive:auto
/devices/platform/tegra-xhci/usb3/3-1/3-1.1/3-1.1:1.0 auto vfat defaults voldmanaged=usbdrive:auto
### usbdrive2
/devices/platform/tegra-xhci/usb2/2-2/2-2.2/2-2.2:1.0 auto vfat defaults voldmanaged=usbdrive2:auto
/devices/platform/tegra-xhci/usb3/3-1/3-1.2/3-1.2:1.0 auto vfat defaults voldmanaged=usbdrive2:auto

## config#2(OTG cable attached before boot)
### usbdrive2
/devices/platform/tegra-xhci/usb3/3-2/3-2.1/3-2.1:1.0 auto vfat defaults voldmanaged=usbdrive2:auto
/devices/platform/tegra-xhci/usb4/4-1/4-1.1/4-1.1:1.0 auto vfat defaults voldmanaged=usbdrive2:auto
### usbdrive
/devices/platform/tegra-xhci/usb3/3-2/3-2.2/3-2.2:1.0 auto vfat defaults voldmanaged=usbdrive:auto
/devices/platform/tegra-xhci/usb4/4-1/4-1.2/4-1.2:1.0 auto vfat defaults voldmanaged=usbdrive:auto

# P1963-C00 IO board
## config#1
### usbdrive
/devices/platform/tegra-xhci/usb2/2-2/2-2:1.0 auto vfat defaults voldmanaged=usbdrive:auto
/devices/platform/tegra-xhci/usb3/3-1/3-1:1.0 auto vfat defaults voldmanaged=usbdrive:auto
### usbdrive2
/devices/platform/tegra-xhci/usb2/2-3/2-3:1.0 auto vfat defaults voldmanaged=usbdrive2:auto
/devices/platform/tegra-xhci/usb3/3-2/3-2:1.0 auto vfat defaults voldmanaged=usbdrive2:auto

## config#2(OTG cable attached before boot)
### usbdrive2
/devices/platform/tegra-xhci/usb3/3-2/3-2:1.0 auto vfat defaults voldmanaged=usbdrive2:auto
/devices/platform/tegra-xhci/usb4/4-1/4-1:1.0 auto vfat defaults voldmanaged=usbdrive2:auto
### usbdrive
/devices/platform/tegra-xhci/usb3/3-3/3-3:1.0 auto vfat defaults voldmanaged=usbdrive:auto
/devices/platform/tegra-xhci/usb4/4-2/4-2:1.0 auto vfat defaults voldmanaged=usbdrive:auto

#usbdrive3
## OTG Host
/devices/tegra-ehci.0 auto vfat defaults voldmanaged=usbdrive3:auto

/dev/block/zram0 none swap defaults zramsize=536870912
/dev/block/platform/tegra-sata.0/by-name/RP2 /persistent emmc defaults defaults

Here's the 16gb recovery.fstab:

# Android fstab file.
#<src> <mnt_point> <type> <mnt_flags> <fs_mgr_flags>
# The filesystem that contains the filesystem checker binary (typically /system) cannot
# specify MF_CHECK, and must come before any filesystems that do specify MF_CHECK

/dev/block/platform/sdhci-tegra.3/by-name/APP /system ext4 ro wait
/dev/block/platform/sdhci-tegra.3/by-name/CAC /cache ext4 noatime,nosuid,nodev,data=writeback,nodelalloc wait
/dev/block/platform/sdhci-tegra.3/by-name/LNX /boot emmc defaults defaults
/dev/block/platform/sdhci-tegra.3/by-name/MSC /misc emmc defaults defaults
/dev/block/platform/sdhci-tegra.3/by-name/UDA /data ext4 noatime,nosuid,nodev,data=writeback,noauto_da_alloc wait,check,encryptable=/dev/block/platform/sdhci-tegra.3/by-name/MDA
/dev/block/platform/sdhci-tegra.3/by-name/USP /staging emmc defaults defaults
/dev/block/platform/sdhci-tegra.3/by-name/MDA /metadata emmc defaults defaults
/dev/block/platform/sdhci-tegra.3/by-name/SOS /recovery emmc defaults defaults
/devices/platform/sdhci-tegra.0/mmc_host/mmc2 auto vfat defaults voldmanaged=sdcard1:auto
/devices/platform/tegra-xhci auto vfat defaults voldmanaged=usbdrive:auto
/dev/block/platform/sdhci-tegra.0/by-num/p1 /sdcard vfat defaults recoveryonly
/dev/block/platform/sdhci-tegra.3/by-name/BMP /bmps emmc defaults recoveryonly
/dev/block/zram0 none swap defaults zramsize=536870912

You can now see why it wouldn't mount your partitions. Someone needs to create a separate recovery for the 500GB model.

edit: looks like Steel01 is trying to make one recovery cover both models. Good luck :)