Hello again!
Unfortunately, importing T3D files was deprecated from UE4 onwards. Unless you are currently working on UE3, we will need a workaround.
Checking around the community, it seems the best approach is to directly replace the contents of your fixed file, into one already inside the project, like this:
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Open the fixed .t3d in notepad, and copy its entire content
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Create a new PhysicsAsset
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Edit it on viewport, and paste the text from your clipboard
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Save the asset, and then use it to replace the corrupted one