Wood screw pulled it's thread out of the dowel:

I drilled it out and fitted a hex bolt with lock nut:

It probably broke because it doesn't always have support underneath it, depending on the bike it's on, and when I carry it off the bike I often do so by holding onto the dowel with the flap open. The bolt should make it a fair bit stronger.
Pics of the new bolt head vs the original screw on the other end:


