Stretch gone bad!

[ItayGal]

I have several Pi's with Raspbian stretch installed. sometimes some of them (not sure if there's any rules) are stuck on a login screen (my image has auto login).

IMG_20180718_143151.jpg (144.13 KiB) Viewed 331 times

and even when i put the correct password they just reboot and come back to this screen.
Nothing helps. only re imaging the cards resolves this issue.
any ideas?

[B.Goode]

any ideas?

Inadequate free space left on the root filesystem?

[ItayGal]

B. Goode, seems like you nailed it!

Thanks!!!