I think the bug has changed a little bit since my first post.

The toolbar.ini shows this line after saving:
n39="girclagbar","Gamers.IRC Lagbar",0,"@lagbar",0,0,0,0,0,0,0,"/lagbar_refresh1","@toolbar_lagbar1",0,1,0,0,"bin\grc\gamersirc.grc"
As I said, the error message is this:
* /toolbar: no such file 'D:\IRC\Gamers.IRC 5.21\@lagbar'

I use this button as lag bar, so the script is a bit large. If you want, I can send you our script to test this bug.

However, I made an abridged version for you to reproduce it with mIRC version 6.32

Code:
alias lagbar_refresh1 {
  echo -a lclick test
}
menu @toolbar_lagbar1 {
  test:echo -a menu test
}
alias toolbar_build1 {
  window -c @lagbar
  toolbar -r
  window -phB +dL @lagbar 332 23 121 19
  drawrect -hrf @lagbar 0 1 0 0 121 19
  window -h @lagbar
  toolbar -au girclagbar "Gamers.IRC Lagbar" @lagbar /lagbar_refresh1 @toolbar_lagbar1
}

In order to test it:
/toolbar_build1
/toolbar -fs
/toolbar -fl

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