Issue shifting from largest cog to second largest

Can you put your bike in a stand and shift while turning the crankset forwards? While not the main issue that you're having, shifting while not pedalling will always make it worse. Eagle drivetrains never shift particularly well into or out of the biggest cog at the best of times.

Did you tune your shifting with the bike upside down on the floor like in the video? Did you tune it to shift into the big cog by clicking the shifter while the pedals weren't turning, then turning them? If so, you probably just need to reduce the cable tension a little.

Either the derailleur is sticking when at it's most inboard position, i.e. on the largest sprocket, or the shift cable is sticking in the housing somewhere.

It's not surprising that the derailleur will eventually shift up when on the trail, it's being shaken and vibrated by trail irregularities which overcomes the stickiness.

Fiddling with the barrel adjuster will not do anything. The cable is payed out from the shifter when changing to higher gears so it can't pull the derailleur outward. The barrel only adjusts the length of cable and hence position of the derailleur not the cable tension in any case.

You want to figure where the stickiness is. Detach the shift cable from the derailleur. With the bike on a work stand or inverted, push the derailleur manually while pedaling to change gear (it really helps to have a friend pedal for you, and be really careful to keep your fingers out of the chain). If the derailleur sticks in the lowest gear there's the problem.

You can also hold the shift cable with a pair of pliers, put some tension on it and work the shifter, you may be able to feel some resistance.

I've never encountered a malfunctioning new derailleur. If the derailleur is sticking perhaps working it through it's range of motion a few times will free it up. Look for dirt, dried lube or anything in the parallelogram that might be binding it up.

Old, dirty cable can develop excess resistance and stickiness, The solution is to replace them, but your's are obviously new. Perhaps pull the cable out of the housing, give it a wipe down and add a little lube.

Have seen this only once before. It was the upper limit screw "marked L on the derailleur body" was too tight. When you shift into the large ring the chain wedges into the ring and is held by the limit screw. That is why shifting twice to a higher gear pops it loose. It increases the derailleur spring tension and overcomes the "jam", Loosen the limit screw 1/2 turn. Be sure you are not crosschaining (big ring front to big ring rear). It compounds the "sticky shifting" issue.

I agree with w Cliff, check the hanger... 1x12 NX is fragile, and temperamental. Must be set precisely. You may have done everything correctly, but have an untrue hanger... in your 2 hours of rip roaring riding, did you strike your derailuer on any rock, root beds, or doorframeS? I understand your frustration, sometimes you have it right... but it can’t be ‘right’ , due to bad hanger. Hope this helps, I know I’ve made that error myself. I’m suprised to hear a sketchy problem with a Canyon. Check it out, it could be that simple.

I would honestly just take the cable off the and use your thumb to push the derailleur into the biggest gear while turning the peddles. do this over and over again. if it ever sticks then you know its your derailleur. if it does not stick you can move on and look into cable issues.....

hope this helps.

I have a Sram Force1 1X11 with e*13 9-42 cassette. I had the issue that I had to tug a little bit on my shift cable to get the derailer out of the biggest cog to the second one.

I tried new cables, I shortened the cable housings as much as possible but it didn't help. It was clear that the issue is in the friction of the housing so i can't do anything about it, so I played around with the derailer clearing set screw (idk how it's actually called) and that helped a little bit.

What did the trick in the end was shortening the chain two links so the whole system has some more tension on it! So check if it's possible to shorten your chain a little bit. My system shifts perfectly now! :)