BusyBox Installation Failure

[AC Question]

I'm trying to install BusyBox via Meefik's installer, but when I run it it shows:

Remounting /system to rw ... done
Copying busybox to /system/xbin ... fail
Setting permissions ... done
Installing new applets ... fail
Remounting /system to ro ... done
.

Then when I go to SuperSU and view the logs, it says

"cp:write error: No space left on device" after the copying to /system/xbin failure, and
"Segmentation fault" after the installing new applets failure

Any help is appreciated!