Triangle cord locks broke right away.  It might be the new grade of PETG being more brittle.

Going back to the CAD file, the problem is the sharp corners of the triangles.  PLA is going to creep.  The entrance to each triangle could be routed  such that more material could line the corners.  

Ideally, the triangle points would face out, the strings would enter a common opening in the middle & fan out.  Then an eccentric piece would overlap the middle & rotate to press the strings into the triangle points.  It's not geometrically favorable.

The next design held up.  They definitely had chakram appeal but were quite bulky.  They're the same diameter as the old design.  Then started wondering if they should be mirror images, so the inner triangles engage the string more.  It would only benefit 2 holes.