Shrinking Handle Scales

So after not using my Fujiwara Teruyasu cleaver for a couple of weeks (and one international plane flight from NY to Australia) I pulled it out to find that the scales on the handle have shrunk quite significantly. On one side there is now roughly 1mm of exposed metal on both the top and bottom of the handle, which is noticeable when you grip the handle (this is a full exposed tang western style handle).

My question is: what would be the best way to reverse this shrinkage?

I briefly tried rubbing some oil into the scales as I would do with a wooden chopping board but they didn't seem to want to absorb much of it. Perhaps the wood is just denser than I am used to and I should soak them for longer? But I'm not sure if there is something else I need to be doing. Would it be a bad idea to soak the scale overnight in mineral oil? This seems like the obvious way to ensure that they absorb as much oil as they possibly can.

Wood will swell and shrink in response to changes in relative humidity. Going from NY to Australia may be a big change which caused the shrinkage. To lessen the shrinkage, ideally you'd let the wood reach equilibrium in the location where you plan to keep the knife then install and shape the scales. If the wood wasn't totally dried to equilibrium, that could also be a reason why they shrunk. You'd also still have the possibility of movement due to seasonal humidity changes throughout the year though.

Even stabilized woods can move, just not as much usually. So one strategy is to use stabilized wood or woods that are naturally stable, often dense oily woods.

What kind of wood is it and did you install them yourself?

I think you'd be fine to soak the handle in mineral oil though whether it will swell up enough isn't something you can tell beforehand. It will absorb more through the end grain, but the majority of scales aren't cut that way since that way leads to weaker scales.