Using the 4.0.9 version, 64 bit.
I think the options Flip Horizontally and Flip Vertically are switched. Both for layer and image editing, the icon indicates what your want to do, but the text says the opposite.
The screenshot below is showing the layer menu. Note how the icon for the 'Flip horizont' is different to the text. Same thing goes for the Flip vertical option.
Same thing goes for the image menu