@Vicky_Bilaniuk this might be what is happening.
That extruder doesn’t look anything like mine. Their modified one does, though. Mine just goes straight down, like their modified one.
Although I lack the spring. I’m going to try raising the nozzle a bit first and if that doesn’t work I will try something more complicated.
I.am printing ninja flex on my ubis hot end, you must have 0 place for it to buckle, you must have the nozel primed. I don’t use retraction…
I’ve not found any particular challenges printing ninjaflex from a hotend/thermodynamics standpoint.
This confuses the shit out of me, because ninjaflex is probably the “stickiest” filament I’ve ever played with, it will stick to anything including your fingers when molten. (3/10 would not reccomend touching molten ninjaflex with bare skin to others). By all estimation it should stick inside a hotend like hell - but it doesn’t.
Surface energies, mu, adhesion of TPU in semi molten state, weird coating applied to ninjaflex. Too many variables, it’s all witchcraft. However I do know that it works, and pretty damn well too.
I agree with the multitude of others here, that your first layer is probably too low, causing too much backpressure. The super-adhesion of kapton and TPU may actually be detrimental here too.
If you want easy printing with ok results try 230-235C where flow is easiest. This will get you stringy but less finicky prints. Then start tuning retraction up and temperature down to reduce strings and improve surface finish. We ended up around 223C, 1.4mm retractions, 13mm/s for the best possible quality.
Post a picture of your first layer attempts and I’m sure we’ll be able to give some much more useful advice.
Also, the ecksbot hotend is a little unconventional, slightly odd formfactor, uses nichrome, and is maybe a bit optimistic from a heatsinking/cooling perspective. But fundamentally it should work just fine from what I can see as long as their manufacturing standards are up to scratch.
Thanks so much. I had to set it aside for today. I will be back at it probably tomorrow. I will post with updates.
Awesome group, by the way.
OK I’m convinced I’ve knocked something out of balance. I increased the z-offset and this actually helped considerably, except only on one half of the plate (and it prints very normally on that one half). So I guess I need to go through all of the balancing instructions. It’s good - I should learn how to properly baby this thing, lol.
This stuff’s hard on the kapton, though. Ouch. Oh and I’ve touched it molten I don’t know how many times. It’s an interesting experience.
This is why I had to install auto bed leveling, it eliminates these types of errors.
OK I rebalanced much more carefully this time and I even adjusted the endstop very slightly and am now printing with no z-offset. Probably shouldn’t have made that last adjustment. 
I think it’s a tad too high now. I’ll have to adjust it back down for when I print ABS because I don’t think I’ll get good first layer adhesion to the plate now. But holy heck is the NinjaFlex ever happy. It very much likes not having any pressure.
Pretty cool watching it go. Thanks so much for all the help!
@Nuker_Bot_NukerBot_3 what exactly did you install? My interest level is rising.