A moringa tree with problems

Hello :)

I hope I've posted this in the right thread (I'm not very forum-savvy at all).

I have a Moringa tree that I planted around 4 years ago. It was doing ok but has, for the past few years, had this disease and/or bug attacking it. I've waited, hoping it can cope on it's own. It kind of has - the main stem has a lot of damage (as shown in the pictures) and the newest (thinner, green) stem was free of it until recently, when I noticed a small bit starting there too.

I have no idea what this is and so no idea what I can do about it. Any suggestions would be most appreciated!

Relevant details:

Plant: Moringa (Moringa oleifera)
Location: Perth, Western Australia, Australia
Climate: Temperate (getting hotter every year)

Those look like teeth marks to me, like someone is gnawing at the bark. Every part of moringa is edible (maybe not the wood), so this doesn't totally surprise me. Can you put some sort of collar around the base of the trunk to stop critters from climbing up? We use stainless steel sleeves on power poles over here to keep possums from climbing them and shorting out the lines.

[EDIT] I had a closer look and saw what appeared to be a snail trail on the unmarred branch. That could definitely be snail damage, too. You can try bands or wires of dissimilar metal wrapped around the trunk are a deterrent, as they set up an electric current when a snail or slug contacts both at the same time. One galvanised steel and one copper about 1 cm apart should do the trick.

This might be helpful for you to read,

https://www.cabidigitallibrary.org/doi/pdf/10.5555/20173063461

I have noticed that it isn't an easy link to access.  I wasn't aware of that when I made the post, but it does contain good information.  Have you hugged a tree today?