Thornless blackberries have something wrong...

They are from cuttings and have been roaming around one of our gardens putting down tip roots for a few years now and have never produced a lot but I thought this was due to my shotloose pruning.
This year I spent some time disentangling them and even staking some as they tend to shoot off sideways.

I've been noticing some are leafing out and some are not and finally noticed that above this 'knot' on many of the canes all was dead but below it leafing out as normal.

Seems familiar like I should know this one?

If it's a disease they'll be removed...if an insect I might wait it out as I doubt it would bother any other garden things and we don't have other brambles near by.

Does this look familiar to anyone?

Galls?  

Our local galls are caused by insects (usually the good kind that eat the nasty insects).  This kind doesn't hurt the plant overall but may decrease berry production on that cain.

But there can be a lot of causes depending on where you are.  Some are pretty bad for the plant.  

Do you know if the blackberry knot gall wasp is found in your area?

A very specifically named insect because it does a very specific thing to a very specific plant. I love scientists haha.

Another culprit could be the rednecked cane borer.

I have also heard of bacterial galls but I believe they are found moreso at the crown than the cane.

Lots of potential causes. I'm not qualified enough to know the true cause. I'm fascinated!

I would also suggest some sort of insect pest.

rose stem girdler

source

I suspect the same advice applies:

Management focuses on good plant health (proper fertilization and irrigation), sanitation (removal and destruction of infested canes)

and killing adults prior to egg laying.
Maybe removing (and destroying) the affected canes will interrupt the cycle, but if endemic in the area I guess they'll come back again unless a suitable predator turns up and tips the balance in your favour.

I have seen some of this if planted close to cedar trees as well. Cedar rust galls affect not only my apples but other trees as well.

My observations: You found them When you began to train them up rather than let them form a thicket. This is what I have noticed that I find them where crowns are large or close together.  Perhaps because I maintain a high population of paper wasps they avoid detection before entering deep into the cane.  I also noted more decline and loss of less vigorous vines like raspberries, loganberries and Boysenberries  when I allowed tall weeds to surround the crowns.
My winters are milled enough to train them  before the tip root and the borers emerge but age is diminishing my productivity. Any one want to come learn skills to inherit property?

Thanks everyone!

It's looking like it's the cane bore for sure

I read elsewhere that the larva travels up and down the cane so I think I need to do some more drastic pruning...and keep the area better tended.