Swamped

In general, when things are affected by the same spell, the ether tends to remain linked even if they're physically separated. The link is something you've had trouble explaining to non-wizards, because it doesn't 'link' in most of the ways they think of; for instance, if you cast a spell on one thing, it won't usually affect the thing it's linked to. It's possible to use a link in that way, of course, but you really have to know what you're doing.

The main impact of the link is when it breaks, which can happen if the objects are moved far enough apart. In a case like this, where it's a person and one of their possessions, the person is usually fine due to having most of the ether on them, so it's able to remain stable. But the possession doesn't usually fare so well. The ether tends to go out of control.

Even that isn't so bad most of the time, since the whole problem is that there isn't that much ether in the first place. The object rarely survives the process, but additional damage tends to be limited.

The main exception is when dealing with fire magic. After all, fire still burns once the ether has left it. Even a small flame can cause a lot of problems if it's not put out swiftly.

So what happens when an object leaks time? It's hard to even wrap your head around. But the most benign possibility you can see is nearby objects moving through time at different rates. And even that's no small matter when you're on a ship, which is always moving around. Get out of sync with the ship's time and you'll constantly be in different places. You'd be lucky to get through that with only seasickness.

That's the benign option. Everything else you can imagine is far worse. Nearby people and objects might be pulled through time, or perhaps remain in the present, but sent to places they were in the past, or will be in the future.

If you'd only realized, you could have prevented it. Right now, your best hope is that either the reaction hasn't happened yet, or that whoever returned the soldier to his own time took care of the mask as well. If not... well, you'll have to think of something when you get there.

But you can already tell, as you near the infirmary, that something's gone wrong.