Did this water heater work in the pass? The symptoms are not consistent with the parts you replaced and would be more consistent with an orifice someone had drilled out or an orificie that is the wrong size, or a flame tube that is misaligned so the gas does not go straight down the tube, etc.
It would have been possible to check the pressure at the orifice, although that was never likely to be the problem.
If the water heater looked just like it does in your video when you first fired it up, it is obvious that it has been taken apart (no insult intended).
The orifice is in place in the orifice holder right? The orifice is that little brass piece that can be screwed out. Just shooting in the dark here as there has to be a very simple answer to this problem and I have seen units where the orifice was lost. Not crossed threaded. That is the single piece that controls the gas flow at a given pressure and since everything else is working as normal, you have reason is believe the pressure is good.
Steve and Andra
2012 F350 6.2 gasser SRW LB
Fab Fours front and rear in case we run into a rhino
2019 Northstar Laredo SC