Windows cannot be closed after opening with :sp on FakeVim

Every time I open a new Editor Window using :sp on FakeVim mode it behaves totally strange.

If I close with :q instead of closing the split it will unload the buffer and both windows will be empty.
What is even worse, even if I click the X in the corner the (sub)windows cannot be closed but rather unload the buffer. Having to restart QtCreator to get rid of subwindows is a bit annoying.

..but thanks for the support of more commands in the FakeVim