When Mitchell is examining the rock wall near the flames, the stone compresses under his hand and that section of the wall moves.
As SG-1 and the librarian finish passing through the time-displacement trap, on a wide-angle shot you can see the path clearly worn in the dirt; obviously, the take used in the final cut was not one of the first ones.
When negotiating the "time-dilation field", one of the persons "frozen" in time sways back and forth, revealing he is just an actor trying to stand still.
Technically speaking, the "dragon" is a wyvern, a two-legged dragon. In mythology and heraldry, most dragons have four legs.
In negotiating the time-dilation trap, Carter makes several basic misjudgments which are unlikely given the character's intellect and combat experience.
She realises that inanimate objects can be used to identify a safe path through the trap, yet decides to use individual rocks instead of handfuls of the sand/soil which would scatter and provide a much more accurate outline of the safe path.
The second rock she throws gets "stuck" in mid-air and she immediately proclaims that it is a dead-end, however the rock only indicates where a "wall" exists. There could easily be a junction at that point, or the path of the throw could have been mere degrees off the safe path.
She assumes that all of the path junctions are at 90 degrees to the previous safe route, and that the safe path has no deviations, low overhangs, or tripping hazards. She proceeds quickly leading the team with no regard for the potential for the entire team to become trapped.