I believe I have got a fix for PETG print. I ended up modifying the handle slightly as to not bind up and now it locks in great for me. I can do another remix or I could send you the file to try out and maybe add to the files if you would like.
Also reading your other comment about the z-axis support bracket I have designed z-axis support in Fusion 360 that also contains a top mount spool holder that I have not uploaded to Thingiverse yet I can send you this file as well if you would like to check it out. I wouldn't mind an engineers eye to see if you can spot any flaws with the design for strength.
It uses half-inch rod threaded 1/2-13 on each end or can use all thread 1/2-13 rod instead if one doesn't have access to threading dies.
P.S. I just noticed the (add file) button on here I will try it out.
Note the Z brace was one of the very first things I ever made with Fusion 360 it is a mess of sketches and extrusions and it was modelled in Imperial sizes. And since its a bit of a mess, my laptop running an I5 processor does take some time to open the model as well.