In the Mountaineering section of www.merelyafleshwound.com I have a link called 'Peak Log' which is an internal html file that opens in a new tab.
When I name the peak log folder '0.peak-log' (placing it first in the mega menu)... every gallery and folder link under 'Mountaineering' on the mega menu opens in a new tab.
When I name the peak log folder '9.peak-log' (placing last in the mega menu)... the gallery and folder links open correctly within the site.