Hey,
I'm currently working with the WS2811 Led Stripes and own 2 for my room. One Pixel(3 LEDs) shine always when I connect the power to the strip, even when the NodeMCU is disconnected. The soldering point of the chip for the Pixel looks good. The other Pixels after it, it is the 30th pixel, work just fine as well. Do you have any idea what my problem could be? The other strip works just fine with the same connections, even when I flip the 2 stripes.
Do you have any idea what my problem could be?
A broken strip perhaps.
Thanks, but I've hoped to find a solution. I thought about the strip being dead 
If the fault disappears when the strips are swapped out, the. That suggest to me the strip is broken.
What sort of solution were you hoping for? Connecting it up with the blood of a bat under a full moon?
You can buy a new strip or try and fix the strip by replacing either the faulty LED or the one before it. Or you can cut out the faulty LED from the strip.
Why are you being so rude? Maybe somebody with a bit more knowledge than me would have responded and told me to check a specific solder connection again, or to reflow the solder on pin XYZ of the chip and then the red Pixel disappears. I certainly know that I can cut out the pixel or buy a new strip, what would be a dumb idea because the rest of the strip works just fine, but I'm aware of this possibility. Thanks
Maybe somebody with a bit more knowledge than
youand me would have responded and told me to check a specific solder connection again, or to reflow the solder on pin XYZ of the chip and then the red Pixel disappears.
The quality of an answer reflects the quality of your question.
You didn’t post a schematic, code or photograph of your wiring. So I knew little about what you had done. I did know you have swapped out the strip and the fault went away so is did seem rather improbable that it was anything else but a faulty strip. The fact that the LEDs worked up stream and down stream of this faulty one says there is no chance that this is a soldering problem, which is why I didn’t suggest it could be.
I assume you didn’t even read the how to use this forum sticky post, which tells you how to ask a question round here.
Once you have written and had published five books and had over 400 electronics and computer articles published, then maybe we can be considered at the same level of knowledge.
+1 to Mike. 
Can't fault his explanation.
Firstly I'd like to apologize that I answered so harsh but I thought that you aren't taking my problem seriously. I was furious and I'd like to excuse myself once again. I just hoped that there is another more simple solution and wasn't quite pleased with the answer:
Grumpy_Mike:
Connecting it up with the blood of a bat under a full moon?
My problem with this strip is that it has worked already, without the Pixel doing this weird thing, so I suggested the soldering thing again. If there can't be any other variable that could have caused this behavior than I am sorry to have bothered you. Thanks again for all your help, even when I was so rude to you.
P.S:
I do have read the forum sticky post, that's the reason why I posted this Topic.
Given that you have indeed done two specific tests, them we must conclude the chip is faulty.
First test: Same code, alternative LED strip of the same dimension. If that works fine, the code is clearly correct.
Second test: Strip that has the problem, simplified code correctly specifying the total number of LEDs to illuminate all white. If all light white except the particular one, it does demonstrate that that one is faulty. Variant of this is to specify a number of LEDs a few short of the total length and see whether that specific number of LEDs is activated.
So these LEDs have four terminals. If either data in or data out was not connected, the data would not flow through to successive LEDs.
It is I suppose remotely possible that if the ground connection was not connected, that the chip may be "phantom powered" sufficiently to on the one hand pass data through and on the other hand, glow faintly red. It would be red because that is the colour with the lowest threshold voltage and it would be faint because it was only powered from the data input. I refer to the ground connection being faulty as the LEDs are referenced to the Vcc connection so can only possibly be powered if Vcc is actually connected.
Since you have checked the soldering and tested continuity between the ground connection of the strip and the solder on the particular chip, such a fault would necessarily be internal to the LED chip and - unable to be repaired. 
Thanks, Paul for the specific information that you gave in your post.
I did all these tests that you mentioned but the error is, as mentioned, appearing as soon as the strip gets power, no matter what I do, but I will take a third look at this section of the strip and try finding any weird spots and fixing them as needed. I have nothing to lose when the chip is broken as you all already mentioned.
I will notify you when I have news(good or bad).