Latest Yocto branch compatability (Kirkstone)

Hello, I am using the Voxl and I would like to use an upstream version of Yocto, specifically the Kirkstone branch. I noticed that Voxl is built with v2.0.3 Jethro branch (which was released in 2016). I tried to use the Kirkstone branch to generate my own rootfs, but these meta layers are too old to use on Kirkstone and I get a bunch of bitbake parsing errors. As a workaround, I tried to use a built-in machine type of the dragonboard-820c, which has the same chipset arch as the voxl. I successfully generated a rootfs (using core-image-minimal-dev as a baseline). I converted the Yocto generated ext3 to and android sparse image format (using android-simg2img) and substituted this new rootfs (now called core-image-min-dev-sysfs.ext3) with apq8096-sysfs.ext4 in the voxl_platform_3.8.0-0.7/system-image and renamed the SYSTEM variable within flash-system-image.sh to core-image-min-dev-sysfs.ext3.

After doing this, I soft-bricked the Voxl and had to manually put it in fastboot so I could reflash the original apq8096-sysfs.ext4 on the unit. I'm I doing something wrong here? Is it an issue that I am using an ext3 sysfs vs and ext4 (I thought it would be okay since its on its own partition)?

Any help here would be greatly appreciated!