So, I thought I would make a post if someone is interested about what is happening exactly behind the scenes.
The way a factory reset works, is that the CID destroys the superblock on it's home partition, which contains all the user data.
What is supposed to happen, is that during boot, the CID is supposed to check if the partition is intact, and if not, it should reformat it.
In all 2019 firmware so far, this reformatting part doesn't work.
This is the command that runs to reformat the home partition and the error it returns:
Code:
# mkfs -T ext3 /dev/home-partition
mkfs.ext2: symbol lookup error: mkfs.ext2: undefined symbol: test_io_backing_manager
Since it can't reformat the home partition, it will result in /home staying unmounted and all of your user data going to ramdisk.
This also results in a lost cell APN, which will cause cell not to work in Europe and possibly some cars in NA.
The service center should be capable of fixing this issue remotely and has done it in my case.
Hopefully Tesla fixes this issue soon...