I cannot upgrade to lollipop on my shield

So, I have an Nvidia Shield Portable and tried to install the lollipop images (update 103 & 106) but when trying to flash system.img I get remote: insufficient memory and flash fails. Everything else flashes fine. I return to factory images manually and all flash fine (as system.img is 100mb less than lollipop) i even lock the bootloader. I then get every official update up until update 101 then I don't get anymore updates, checked for weeks. Can anyone help? Thanks

(Not my first Rodeo, but tried reformatting and repairing system partitions in twrp (which report plenty of space for update) but still fails)