IIRC, that happened with the early switch docks as well - some after market chargers and cables screwed with voltage negotiation
Fun facts on the new monitor/DP cables/overclocking
Both monitors support 60Hz 10 bit, but when overclocked lose the 10 bit option
Reducing the blanking pixels can let me OC to 69Hz on both displays (Nice)
buuuuuuuut - they get that Vsync off 'tearing' effect so much worse.
Stock 60Hz + 10 bit, Vsync off at 120FPS? zero problems. Very minimal tearing if any, at 120FPS
120, 138 or 140FPS at 69Hz? All have tearing.
Makes me wonder if the people obsessed with vsync tearing and related issues are just running monitors that trimmed the fat too much on their signal padding, and would benefit from simply dropping refresh rates (Similar to how samsungs high refresh models have scanline issues, but manually adding 200/165/144/120 solves it)
Edit: Looks like it's all bandwidth related, to an extent.
HDMI on the same display has a lot more padding/blanking pixels, and is stuck to 60Hz 8 bit - technically, 59.996hz
I get the feeling some weirdness with DP to HDMI adaptors and such is all from the fact DP uses 60Hz and HDMI uses 59.996, and some monitors flip flop between then
LG on the left, kogan on the right - both DP
But then look at the LG's stock HDMI values, far more bandwidth used - 10% extra blanking pixels vertically
DP has free bandwidth and can do 65Hz 10 bit on both displays, 66Hz cuts back to 8 bit. (That perfect 10% more, oh woe is me)
CVT-RB2 standard is the one that gives the smoothest result (and seems how the standard timings are resolved) - Exact reduced lets me OC more, but introduces more tearing
Both monitors let me do 65Hz 10 bit from this, and it feels extremely fluid even with Vsync off - there's no tearing (or you have to do specific things like walk sideways past objects horizontally moving the other way at high speed) to see any tearing at all. It's weird seeing 60Hz displays running as well as the 144Hz displays, just because they're older tech with slower response panels/backlights.
Since I'm pretty sure that my JSAUX dock is what killed my first Steam Deck, I went ahead and got the official one.
Hopefully, this one won't have that problem. I'll be using it exclusively with the included power supply, and if I need any more USB PD power supplies, I'll probably get the Steam Deck one from iFixit or something.
My 8 year old saw that and said "Holy crap that's a cool modded switch!"