command line editing and line length problems with serial port

[Dave Bruce]

I'm using busybox 1.00. I connect to the serial port of a TQM8260 via a 
"console management switch". I telnet to that.  I've also tried a direct 
serial connection with same results described below.

The problem that I am having is when using a previously typed in command 
that has been been retrieved by the up arrow key. The character count 
exceeds 79 (including the prompt characters) of the retrieved command. I 
go to the end of the line (Ctrl-a) and left arrow back to the position 
that I want to edit. When moving left hits the 79th character, the 
cursor will move up one line and to the left edge of the screen. If I 
move the cursor to the right, it will display the character that is in 
that position. If a ctrl-l is typed, the screen will clear and the line 
will appear normal.

If there is an extensive history of commands that exceed 79 characters 
and I up arrow through them, the command line moves up one line and 
shows the command until you are at the top of the screen.
The $TERM is 'linux'. I've tried 'vt100' and 'xterm'.

On one occasion I lost use of the shell and tried telneting in but after 
logging in I didn't get a shell.
Not sure how it happened so I have not been able to repeat it...

This does not happen in a telnet session. The TERM defaults to 'xterm'.

Is the problem with busybox or the linux serial line device driver?

This is my shell configuration:
#
# Another Bourne-like Shell
#
CONFIG_FEATURE_SH_IS_ASH=y
# CONFIG_FEATURE_SH_IS_HUSH is not set
# CONFIG_FEATURE_SH_IS_LASH is not set
# CONFIG_FEATURE_SH_IS_MSH is not set
# CONFIG_FEATURE_SH_IS_NONE is not set
CONFIG_ASH=y

#
# Ash Shell Options
#
CONFIG_ASH_JOB_CONTROL=y
CONFIG_ASH_ALIAS=y
CONFIG_ASH_MATH_SUPPORT=y
CONFIG_ASH_MATH_SUPPORT_64=y
CONFIG_ASH_GETOPTS=y
CONFIG_ASH_CMDCMD=y
# CONFIG_ASH_MAIL is not set
# CONFIG_ASH_OPTIMIZE_FOR_SIZE is not set
# CONFIG_ASH_RANDOM_SUPPORT is not set
# CONFIG_HUSH is not set
# CONFIG_LASH is not set
# CONFIG_MSH is not set

#
# Bourne Shell Options
#
# CONFIG_FEATURE_SH_EXTRA_QUIET is not set
# CONFIG_FEATURE_SH_STANDALONE_SHELL is not set
CONFIG_FEATURE_COMMAND_EDITING=y
CONFIG_FEATURE_COMMAND_HISTORY=100
CONFIG_FEATURE_COMMAND_SAVEHISTORY=y
CONFIG_FEATURE_COMMAND_TAB_COMPLETION=y
# CONFIG_FEATURE_COMMAND_USERNAME_COMPLETION is not set
CONFIG_FEATURE_SH_FANCY_PROMPT=y