The one snag on the lander happened when the protective sheath around the robotic arm didn't unwrap all the way after touchdown.

唯一的故障就是在探测器着陆后包围机械手臂的保护罩始终没能打开。

youdao

The device can also include a protective sheath disposed over at least a portion of the elongate shaft and movable relative to the elongate shaft between a distal position and a proximal position.

该设备还包 含置于细长轴的至少一部分上的保护套，且可相对于细长轴在远 端位置和近端位置上移动。

youdao

One is a protective sheath that keeps cells alive for months outside a host body, nourished by a layer of fat.

FORBES: The Science of Small

In MS, the protective sheath or layer around nerves, called myelin, comes under attack which, in turn, leaves the nerves open to damage.

BBC: Simple eye scan can reveal extent of Multiple Sclerosis

With MS, the protective layer around nerves, known as the myelin sheath, becomes damaged.

BBC: Brain scan of MS patient