I'm not allowed to type in more than two characters to do search

- [ ] I have read through https://github.com/junegunn/fzf.vim/blob/master/README.md
- [ ] I have read through https://github.com/junegunn/fzf/blob/master/README-VIM.md
- [ ] I have read through the manual page of fzf (`man fzf`)
- [ ] I have searched through the existing issues

MacOS Catalina
iterm2 Build 3.3.12
neovim v0.4.3
I used vim-plug to install the latest version of fzf-vim.

I pressed s to go to the command line bar and there I can search for text in the current buffer. After the prompt ">", I typed the three characters ":Rg". However, g ended up appearing at the bottom-right corner and the search broke down, marked as in the red box in the following figure. Each time I search for a text, I'm not allowed to type more than two characters. Can one help me solve this issue. My init.vim is attached below.
[init.vim.txt](https://github.com/junegunn/fzf.vim/files/4930673/init.vim.txt)

Thanks in advance!