With vscode-neovim, sometimes causes duplicate text to appear upon exiting insert mode

[BlueDrink9]

Explain the issue

I don't have time to do minimal reproduction or thorough diagnosis, but I'm opening this here so that if other people have a similar issue, they can discover that matchup might be causing it. I hope you don't mind. I suspect it's a complicated interplay between vscode's completion, matchup, and maybe some of the other settings I have.
Possibly related to #325

After using VSCode-neovim for awhile, especially after completing a workspace function suggestion, exiting in certain mode seems to input a second copy of anything that was just inserted.

1. What vim version are you using? If using neovim, Are you using
   tree-sitter or classic matching?
   treesitter, nvim 10.1
2. Steps to reproduce
   -- NA for now
3. Expected behavior
4. Observed behavior

If your issue is instead a feature request or anything else, please
consider if minimal examples and vimrc files might still be relevant.

Minimal working example

Please provide a minimal working example, e.g.,

if l:x == 1
  call one()
elseif l:x == 2
  call two()
else
  call three()
endif

Minimal vimrc file

Please provide a minimal vimrc file that reproduces the issue. The
following should often suffice:

set nocompatible

" load match-up
let &rtp  = '~/.vim/bundle/vim-matchup,' . &rtp
let &rtp .= ',~/.vim/bundle/vim-matchup/after'

" load other plugins, if necessary
" let &rtp = '~/path/to/other/plugin,' . &rtp

filetype plugin indent on
syntax enable

" match-up options go here