Don't have any photos from the cook unfortunately. The BBQ is a bit leaky, but no more than any other Weber kettle I wouldn't have thought. I did notice when the Qmaster was blowing, a fair bit of of smoke was escaping between the lid and the BBQ. I had the vent on the top mostly closed, by opening this a little (which would result in less positive pressure) I'm guessing it would prevent this from happening, but I understand you want this pressure in order for the fan to work effectively. I had all vents other vents completely closed.
Given it was so damn cold outside that weekend, I didn't spend much time keeping an eye on the LCD on the Qmaster. I was mainly watching the pit probe (Inkbird IBT-2X, bluetooth) from the relative comfort (and warmth) of my home. It didn't help that I had the Qmaster in Celsius and the pit probe in Fahrenheit as I was having to use a converter to compare the two. I changed this half way through. I did notice a fairly big difference between the Qmaster temp and the pit probe, even though the probes were in the same spot. I have subsequently calibrated both in boiling water and both were reading the same +/- 1 degree, so not sure what was going on then.
In any case, I can see based on that graph that the fan was coming on when it should have @ ~220. I did change it at various stages, which is why the graph shows the fan turning on at different times in the first few hours. The problem just seems to be that it is staying on for too long? For comparison, do you have a graph of any cooks you've done with the same unit? I'd be interested to see how big your swings are.