I may be overthinking this, but I am wondering if there is a way to tighten this fitting to make sure it doesn't come loose again. Ideas so far:
1) Tighten it some more using my pipe wrench
2) Use some PTFE tape (I know it's to make it watertight, which is not the issue)
3) Apply some loctite (there do seem to be rather a lot of products, maybe this one: https://www.vikingtapes.co.uk/products/loctite-243-threadlocker-blue-medium-strength?variant=40172618940479
4) Find a nut to go on the thread, and then lock it to the fitting (in a similar way to my stern gland)
Many thanks!