Are you possibly using the lower cooking grate on the top?
I thought it might've been that. I tried both of them and they both do the same thing. I'll provide pics ASAP.
As was mentioned above, the two grates are a different size (for the life of me, I cannot come to a logical reason for that)
What he said! If the lid fits well, then it's probably a cooking grate that's a wee bit out of spec. The washer trick will fix it.That one has popped up a few times over the years. Seems to be either an out of round condition or slightly smaller grate.
One easy fix was to use a few washers as shims between the bracket and body.