Wavecom modem can't write

I have a wavecom modem it's been working perfectly until two days ago.
Here's the problem...

screen /dev/tty.usbmodem24111 115200 (no problem)
Ctrl A + Ctrl \ to quit screen.

Try to connect with screen again
screen /dev/tty.usbmodem24111 115200

However this time whatever I type it just won't shows up in the terminal.
If I switch off the modem and turn it on again, the first connection will be success without a problem but once I quit the first connection (screen), the following connection (screen) will have the same problem again.

I also tried this on a serial communication application called coolterm but it yields the same result.

I was doing this on MAC, I've tested in Ubuntu with fresh new install but getting the same result.

However with coolterm on window it doesn't have this problem.

Here's the output of stty -f /dev/tty.usbmodem24111:

speed 9600 baud;
lflags: -icanon -isig -iexten -echo
iflags: -icrnl -ixon -ixany -imaxbel -brkint
oflags: -opost -onlcr -oxtabs
cflags: cs8 -parenb crtscts

If anyone has any clue what is going on please let me know...
I post this on stack overflow but no one respond to it...

I really could use your help, Thanks in advance !