I started thinking again about what you said about your light switch, and thought that might be part of the issue (as I had read somewhere else about a flickering cluster related to faulty light switch) but I re-watched your video and remembered that the warning lights were also flashing (not just the information lights), so now I'm leaning back to the issue not being in your light switch...however if you were having issues with your light switch, now seems as good a time as any to replace it.
Regarding your posted voltages on B1, mine shows a slightly lower reading (.5v) than others (ie B10), but I am not seeing a voltage drop (as you reported) by switching the ignition on, which makes me think it's indeed the ignition....but I thought you just replaced it. Did you check the condition of the wires and connectors when you swapped the switch?
I stated earlier that I reserve the right to change my mind at any time (lol) but now I'm half leaning against a fault in the cluster, but unfortunately, the other half still is.
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