Follow up on my pulsing lights. I swapped in the Victron MPPT 100/30 yesterday and so far, no flickering/pulsing of the interior lights, like I had with the Renogy PWM controller.I had some ceiling light pulsing after I switched to Lithium as well, I don't think that I ever looked at the Renogy Inverter while this was going on, but I did throw a multimeter on the positive and negative 12V distribution blocks and the voltage was moving up and down in a similar fashion to what your video shows.
What I ended up doing was lowering the Renogy PWM charge controller's output from the boost of 14.6V to 12V. The pulsing stopped. I then slowly increased the boost voltage and I hit a point where it started pulsing started again, around 13.5 if I recall correctly. I lowered the boost voltage down a few tenths and the lights seemed to stay steady. This was all during the day, without a cloud in the sky. My batteries have stay well charged so far and I've not had any more pulsing. I'm attributing it to the PWM charge controller, whether it's going bad or just something the PWM does with these particular lithium's, I don't know. I have a Victron MPPT waiting to be installed, so I'll see what happens with that when I set a higher boost voltage.