This is the normal startup message, you see it only when batteries are first added to the mod. Normally one doesn't see it because one tends to hold the mod facing down while putting in batteries, and by the time you've done up the caps and turned it over, it's booted and isn't showing the message.
You've since worked out the problem it seems - you were seeing this message due to poor battery connections which you fixed with clearing out gunk on the tubes/threads.
I think you're the first person we've seen (on this thread/forum) with the black. That clearing of the tubes/threads was something we often had to do with the Kangxin/Waidea flasks but didn't know about re the SXK. Seems it's the same deal there, so thanks for confirming.
It's a shame that it's necessary, but not surprising when one pays $58 for a VF
Some manual work will be needed. Well unless you buy the silver
Nice to be wanted

However I do not believe the issue described by
@Almighty is related to poor ground. The symptoms of poor ground are: saying low battery when it's clearly not low (usually, but not exclusively, while firing); firing but putting out less wattage than it says it is; randomly turning off/not turning on.
Actually the more I think about it the more the issues described by
@Almighty are pretty weird:
This is really odd. I joked higher up about "maybe it's reading the resistance -1.0Ω now!" but this may actually be close to the truth. Not -1.0 of course, but a significant amount.
Because it's clearly reading the atty for these people - it's not saying No Atomizer. So it's reading an atty, it's letting them fire, but it's reading 0.00Ω and saying Low Res.
This does not sound like a wiring/physical problem. It sounds like a worsening of the known resistance/chip problem - to an extreme degree in certain cases.
Two possibilities:
1. They both mistakenly put in a build of 0.04Ω - 0.05Ω (lower than spec) and the usual low reading shows it as 0.00Ω
2. They both put in a build that's within spec (0.06Ω +) and the drop in resistance is showing as even worse for them - at least -0.06Ω potentially much more.
I will find those posts and reply to ask them what they did. Thanks
@Almighty for the heads up (you're just reporting on others' problems, you don't have this issue yourself - right?)