Power injection trouble shooting

I have purchased 8 coreflute candy canes second hand. They have 16 pixels in each cane. I set them up and found I needed power injection to get them all to work. So I injected power at the start, in between cane 4 and 5 and also at the end. This improved things but I was still getting flickering on white. The flickering was also giving a rainbow of colours over a few pixels.

I checked the voltage whilst running at each of the injection points and it was 12.4V. I noticed that the signal started flickering at cane 3, so I moved the injection point from half way and put it before cane 3. Issue solved, no more flickering. Not sure why this is though. I had two thoughts. First that the data signal was somehow diminishing after cane 2 and needed power to boost it back up or alternatively that I had a dodgy connection near cane three and maybe the data/power wasn't getting passed that point very well. It just seemed odd to me that the lights near the injection points were flickering as well as ones further away. I know I probably haven't given all the information required to sort this but any ideas on what to look for would be greatly appreciated. All pixels are 12v ws2811. As I said I've got it going but I'd like to know a likely cause of the problems.

Whilst troubleshooting I moved the injection point at the end to two canes in from the end thinking the power could go both ways with less voltage drop. This made no difference.

Check that you haven't got a broken gnd connection on your pixel interconnect wiring. The power injection wiring sorts the power but having a broken gnd causes a flaky/noisy data signal.

If they were bought pre built I would first be looking for any connectors that may be dodgy.
If the strings were plugged together with the original JST connectors, they aren't waterproof and may be loose or have corrosion in them causing bad signal.
If the strings are soldered together, it may be a bad solder joint.
Also look carefully at any pixels near the problem to see if you have any corrosion in them. i know if the canes are anything like the ones I got you need to stretch the wires a bit to get them in, so may have made a little gap in the seal.

Thanks Alan and Scamper. Hadn't thought about the ground connections. Having said that I have cut and re-soldered every external pigtail connection to make sure they were all good to go. The canes are glued together so did want to cut them apart unless absolutely necessary. Pixels are like these ones https://www.aliexpress.com/store/pr...013.html?spm=2114.12010615.0.0.729da0baAkWcEe but they appear to be resin filled. Will check each cane individually and see if I can narrow done the problem ones.

Thanks again.

I checked all the canes again tonight and can't seem to replicate the issue. This makes me think maybe it was a pigtail not quite connecting cleanly. Is there a way to clean pigtail connections to ensure a good connection. Can you spray them or dip them in some sort of cleaning fluid. Or does unplugging them and plugging them back in a few times do as good a job for getting rid of any tarnish.

plugging in an out a few times might loosen up tarnish, then use one of these type of products to remove it:
https://www.jaycar.com.au/inox-mx3-lubricant-corrosion-inhibitor-can/p/NA1024
https://www.jaycar.com.au/electronic-cleaning-solvent-spray-can/p/NA1004
https://www.jaycar.com.au/contact-cleaner-lubricant-spray-can/p/NA1012

Thanks Ozaz. I'm getting to know our local Jaycar people very well.

i'd use a bit of INOX, great stuff. just use the thin tube in the nozzle and wipe up any excess.