Howdy Mark & Welcome Here !!!!
Bit of a guess as I'm not sure of the exact order of things & the heat you might be running at.....
The spray is not a bad idea, not absolutely necessary, but OK........the cooker will automatically season just by way of cooking various items....
Did you allow the coals in the chimney to burn all the way thru to orange, or even to somewhat ashed over ?
Reason I'm asking these things is, one, the spray may be causing some of this if it's a little thick and two, if your charcoal is partially lit at the start it can be a bit smokier than normal........
Might want to just do one cleanout burn (no food) with a good sized batch of coals, like 1 chimney + some unlit laid across the bottom of the grate.......lite up, pour all across, let it burn for a few, add cooking grate, let it burn for a few, then the lid & just let it go all the way thru 'till the coals burn down.......all vents open........
For higher heat grillings, I try to let the charcoal get good & going before placing the lid......
One other 'slight' possibility is if the charcoal picked up any moisture.....bag open, heavy dew in the morning could be enough to cause a little bit of a problem....it would likely not burn as hot, maybe smoulder, even go out in some places that didn't have good contact with burning coals....