Multiple Defects

[The Rookie]

Hi all! I hope all is well.

I was doing a study today to see the effect of process parameters on a “bubble” defect in PET tubes. I say “bubble” because I’m not sure that I can call it trapped gas or a void yet...It is too small to test with a heat gun to check for expansion or collapse.

Anyways....With pack and hold off, I noticed that a bubble was in the same direction as a flow mark. Not sure what to classify this mark as, but maybe one of you might

In one picture attached, I Sharpied over the bubble and traced the line I observed so it’s easier to see.

The same mark is on each tube, and I can actually feel it when I run my finger along the surface of the tube.

Any ideas on how to resolve this or what the cause might be?