Capsules are special locators that need special connections set up. Simply duplicating the object does not keep or restore these connections on the duplicate object. It is recommended that you always use the Muscle > Muscles/Bones > Make Capsule menu item rather than duplicate existing capsules. See Create a capsule.
If you have duplicated a capsule or muscle that already has a cMuscleObject shape node, you can use the Fix Invalid Muscle Object Nodes menu item to re-create a valid shape, but any old settings on the original shape will be lost. See Fix invalid Muscle Object nodes.
