Check box in WPF appears as black square

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C#

WPF

This is what I mean by checkbox (simplified code to avoid all confusing stuff):

<ToolBar IsManipulationEnabled="False">
                <Menu>
                    <MenuItem Header="Select file">
                        <MenuItem 
                            Click="BtnOpenFile_Click" 
                            IsChecked="{Binding IsFileSelected}" 
                            Header="File"/>
                    </MenuItem>
                </Menu>
            </ToolBar>

Normally WPF checkbox appears as empty or ticked.
For me it appears empty when not ticked (as it should):
https://i.stack.imgur.com/wkPE3.png

Black square when ticked (as it shouldn't):
https://i.stack.imgur.com/eK5aN.png

Normal "tick" when ticked and mouse hovers above (as it should, but all the time):
https://i.stack.imgur.com/kmAr8.png

I'm not using any 3rd party libraries for UI, it's default WPF. Is there a way to fix it? I'm almost certain that black square part is a glitch.

What I have tried:

A lot of googling but no one offers direct working solution.