actually it has 2 version.
- one in /sbin/busybox which link from /sbin/recovery (v1.16.3)
- another one in /system/xbin | /system/bin (v1.19.3)
i noticed that if you run terminal type "busybox" it shows 1.19.3, then after "su" it called /sbin/busybox which is the old version
It makes it impossible for su binary and busybox upgrades to fully stick, since different binaries will be called for superuser, and these will be out of date. In fact, whenever you're in superuser mode, most system critical stuff used is actually symlinks to /sbin/recovery - including /sbin/busybox.
Its a very 'SEMC' $PATH that's set in init.rc - /vendor/bin comes before /system as well.
Since you can't upgrade /sbin/busybox easily, the solution is to fix $PATH ... move /vendor and /sbin to after /system, and the issue should be fixed at the root, hopefully without it all blowing up in your face.
P.S. USB mount in recovery works fine here