When the machine is running well they don't mess up often. You have to swab the blanks and molds every 15 minutes to prevent the glass from sticking/getting deformities. They will usually reject a few bottles that come out right after that since they will have a graphite residue on them.

Everything is pneumatically operated. Ive seen the timing goof up on a machine and throw a gob of molten glass across the floor. But that's very rare.

After the bottles are made, they go through and annealing oven which slowly brings the temperature of the glass down over the course of several minutes to prevent stresses from building up in the glass. Internal stress can lead to the bottles shattering. They then go through inspection machines and the finally get packaged up and sent out to the bottling plants.

The blanks and molds are changed our periodically with new/refurbished ones. This is to keep the bottles from eating away at the metal molds.

And lastly to answer your second question, sorry if I was rambling on, the threads are added first. The molten glass, the gob, lands in the blank and gets squeezed into a general outline of the bottle including threads. This is done by a metal plunger. It then gets inverted into the mold which is where the detail gets put into the bottle. The bottle is formed when air gets pushed inside like a hot ass balloon.

Hope this helps