<https://community.ultimaker.com/topic/19249-how-to-tell-when-the-ptfe-coupler-is-bad/>
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<https://content.invisioncic.com/ultimake/monthly_2017_12/55f8fd6dd33d4.thumb.jpg.42941ac58e097e9c8b7c2631f7ca5738.jpg>
<https://community.ultimaker.com/topic/19249-how-to-tell-when-the-ptfe-coupler-is-bad/>