No cigarette lighter power/flickering rev counter

Just been out to try my dashcam at night time to see what sort of picture quality I get.
I have the cigarette lighter cabling connected to a 12v-5v hard wire kit then to my satnav and an unused dual usb socket. The dashcam charges fine when in its dock, but as soon as I turn my lights on the power cuts on the dashcam.
I also got my rev counter flickering and even going off for about 30 seconds or so, before illuminating again. It doesn't stop working, the LEDs just seem to die.

Am I right in thinking this is a battery issue? Or something else? I'd had the battery on trickle charge for about 3 days prior to this and it doesn't struggle to start up.
Might the negative earth strap be worth a clean too?
Cheers!

Been out again today, and the power is definitely being cutoff even when the sidelights are turned on. Really odd! It's not like it's not drawing enough power, it's like it's not drawing any at all. I'll get a multimeter on it later, but it's very odd!

Got a multimeter on the usb and with lights off i get 5v, then with the lights on i get 0v. I only tapped into the 12v sources on the cigarette lighter but i'm now thinking it maybe associated to the power going to the bulb of the lighter now it's not attached. Who knows!
Checked the battery and it's on 13v, 14v with engine on.

Anyone got any ideas on this?

Well I'm an idiot. If anyone else experiences this problem, make sure you've not used the LED live as your ground. All sorted now! Won't make the same mistake again.