Vigilant II is just humming along!!!
I'm new to coal, but by reading Vigilant II is just humming along I learned all I needed to be a very happy camper. From your description and my brief experience, I would suggest the following:
1) make sure secondary air inlet is closed.
2) make sure all gaskets seal well (door latch is adjustable)
3) slice/shake, but not more than twice per 24 hrs
4) make sure draft is good; check with smoke/flame source at slightly open griddle or secondary inlet
5) make sure ash pan isn't over full, blocking air flow under coal
All above to assure all air is through the coal bed, not over it.
Read above thread again (humming...), and you should be good.
Don't give up! It's fantastic once you get it sorted out!