First keypress of `<C-f>` map key in insertMode not triggered

Describe the bug
InsertMode key mapping for is something wrong!
The first time to press <C-f> did not trigger map keys!

To Reproduce
Steps to reproduce the behavior:

1. change user setting for the plugin as

"vim.leader": ",",
  "vim.useCtrlKeys": true,
  "vim.insertModeKeyBindings": [
      {
          "before": ["<C-f>"],
          "after": ["<right>"]
      }
  ],
  "vim.handleKeys": {
      // "<C-f>": false
  },
  "vim.normalModeKeyBindings": [
      {
          "before": ["<leader>", "w"],
          "commands": [":w"]
      },
      {
          "before": ["<leader>", "f", "l"],
          "commands": ["workbench.action.toggleSidebarVisibility"]
      },
      {
          // "before": ["<leader>", "<leader>", "f"],
          "before": ["<leader>", "<C-f>"],
          "commands": ["editor.action.formatDocument"]
      }
  ]

2. toggle the develop tools
3. open a file with somthing, and press i to change to inserMode
4. press <C-f>
5. press <C-f> again.

Expected behavior
every time pressed <C-f> in insetMode, develop tools debug logs should trigger <right> key.

Screenshots
the first time press <C-f>, it would not trigger <right> key, like this:

over press more than the sceond time for <c-f>, it work!

Environment (please complete the following information):

• Extension (VsCodeVim) version:
• VSCode version: 1.26.1
• OS: maxOS 10.13.6

Additional context
Nothing!

Reproduce the issue with the provided VSCodeVim settings, especially the insertMode mapping from to , and inspect the insert-mode key-mapping handling. Done means the first and every subsequent press triggers the mapped key, with the behavior verified in the VS Code developer tools logs.