Separators missing after opening sidebar

Description

When I open and close the sidebar (e.g. Undotree, NvimTree), the leftmost separator gets replaced with "<". I don't know if this is a bug, or if I had configured it incorrectly.

To Reproduce

init.lua:

  {
    "romgrk/barbar.nvim",
    dependencies = "nvim-web-devicons",
    init = function()
      vim.g.barbar_auto_setup = false
    end,
    version = "^1.0.0",
  },

barbar.lua:

require("barbar").setup {
  custom_colors = true,
  animation = true,
  tabpages = false,
  auto_hide = true,
  clickable = true,
  sidebar_filetypes = {
    NvimTree = { text = "Everything Bagel", align = "center" },
    UndoTree = { text = "UndoTree" },
  },
  preset = "default",
  no_name_title = nil,
  separator = {left = '▎', right = ''},
}

Steps to reproduce the behavior:

Start up your neovim and load a file
Open and close the sidebar (e.g. Undotree)
See error

Screenshots Before opening the sidebar:

After opening and closing the sidebar:

Informations NVIM v0.9.5 Build type: Release LuaJIT 2.1.1710088188

Edit

Looks like there is an extra space appearing from somehere:

%#BufferCurrentSign#%#BufferCurrent# %#DevIconDefaultCurrent# %#BufferCurrent#a%#BufferCurrent# %#BufferCurrent#%#BufferCurrentSignRight#%#BufferInactiveSign#%#BufferInactive# %#BufferInactive# %#BufferInactive#b%#BufferInactive# %#BufferInactive#%#BufferInactiveSignRight#%#BufferInactiveSign#%#BufferInactive# %#BufferInactive# %#BufferInactive#c%#BufferInactive# %#BufferInactive#%#BufferInactiveSignRight#%#BufferTabpageFill# %#BufferTabpageFill# %#BufferCurrentSign#%#BufferCurrent# %#DevIconDefaultCurrent# %#BufferCurrent#a%#BufferCurrent# %#BufferCurrent#%#BufferCurrentSignRight#%#BufferInactiveSign#%#BufferInactive# %#BufferInactive# %#BufferInactive#b%#BufferInactive# %#BufferInactive#%#BufferInactiveSignRight#%#BufferInactiveSign#%#BufferInactive# %#BufferInactive# %#BufferInactive#c%#BufferInactive# %#BufferInactive#%#BufferInactiveSignRight#%#BufferTabpageFill# %#BufferTabpageFill#

romgrk / barbar.nvim

Separators missing after opening sidebar #560

Edit