@user For posterity:
I was using lineageOS prior to this, there was an issue flashing back to android. namely, mke2fs failed because unimplemented ext2 function while setting up superblock
quick google search said I need to go into the flash-all.sh and edit it.
I had to change the last line from fastboot update -w <image.zip> to fastboot update <image.zip>
the -w flag is to wipe userdata and cache.
So far, the image seems to be flashing without issues.