The same character is input twice when I input "/" or "t"

toshimichi@toshimichi ~ $ cat /etc/lsb-release  
DISTRIB_ID=LinuxMint
DISTRIB_RELEASE=18.2
DISTRIB_CODENAME=sonya
DISTRIB_DESCRIPTION="Linux Mint 18.2 Sonya"

I'm not good at writing English, so I decided to tell you how the bug happens by video.

Video: https://youtu.be/zYbVuBBkIRA

No exception was found in the log file.