It is pulling out of the top end of the PEEK.
Destroyer, thank you for the explanation, it makes sense now. If I understand correctly, you are saying assemble it so when it slides out, I can remove the plug, re-assemble it and the white collar should be locked much tighter. After reading your reply, I took a much closer look at the end of the Bowden tube where it has been pulling out. I slid the tube through the collar and you are in fact correct; where it ended it was grabbed much tighter. However, I am struggling to come up with a way to implement your suggestion. The bowden tube does not slowly slide out, but rather pops out very quickly. When it moves, it moves almost 3/4 of an inch or so. This is too much for me to simply allow it to slide slightly, remove the plug, re-tighten the thumb screws, and have it clear the wood and seat nicely in the PEEK.
I tried the toothpick trick and it does help quite a bit but I am still experiencing the same problem to the degree that I cannot print a part. I have ordered calipers and will measure the end of the bowden tube as soon as I receive them as it was suggested it may be too small. Would it be possible to jam the bowden tube onto the brass barb?
Thanks to everyone who has replied. I have been struggling with this every night for over a week (and am starting to get frustrated), so I truly appreciate the constant flow of suggestions to give me new things to try. From what I understand though, the magic fix for this problem is to print the bowden clamp on thingverse. While I am not ready to give up yet, if anyone is willing to print one of these for me I would gladly pay for your time, material, shipping, and a six pack (or even case) of your choice.
Thank you!