a)
The ones in the pilot episode do turns and land upright creating a giant crater,
the ones in episode three literally landed in a straight line, upside down, and without making any kind of crater, they couldn't be more different.
B)It makes sense, imagine you're Cyn, your objective is to destroy the solver drones, destroy the patch and then the planet, what do you do?
1) You arrive with your army of disassembler drones.
2) You deploy them while you stay safe.
3) They kill the worker drones and, along with them, the solver drones.
4) When they finish with their designated area, they go to the lab, find the cure, and destroy it.
5) You land and destroy the planet. Easy.
The problem is that they keep failing completely when trying to enter the lab.
Then Doll, a solver drone, appears, searching for the cure and seemingly knowing its location. What do you do?
You go down in disguise and, under the pretext of also wanting to destroy Cyn, manipulate her into leading you inside the labs to the cure. Then you kill her, destroy the cure, and mission accomplished.
At least that's how I understood it.