I could've sworn I was able to run into an enemies bubble, tether and make it go away. But I just had a match today where I tethered enemies inside their own bubble and they were still shielded. There were only 2 titans in the opposing team and they were both tethered. Bubble still up. I have video if you need more proof. Working as intended?
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If you use quiver you can break the bubble by shooting 3 different spots. Or you can shoot the same spot twice and "split the arrow" and it will go inside the bubble and tether enemies.