How does damage from surgical instrumentation during implantation occurs?

I would think the easiest way to damage the implant is during the closure. You now have a vulnerable implant bulging out of the incision and the surgeon has to get that incision closed, and closed with enough thickness of tissue so that even in a thin-skinned patient, it will heal with strength, very challenging. If you have the incision edges pulled back by an assistant and then insert the semicircular needle it might hit the implant, or if the needle tip is not visualized at all times it might hit the implant without you knowing it. Then later when they examine the implant under a microscope it shows the telltale signs of a needle wound.
To minimize the anxiety and chance of implant injury during incision closure I use a pediatric fish as well as a double-ended metal spoon retractor to protect the implant. The fish is a silicone elongated fish like shape device with a string and plastic ring attached to one end. You slide it in the incision and it completely covers and submerges the implant, keeps it completely out of the way. Then you place the sutures under direct vision with the metal spoon retractor as a barrier between the needle tip and fish, because the needle could go through the fish, potentially. The needle can then continue across and over the fish to the other skin edge and up where it can be grasped, or the stitch can be done one edge and then the other separately with or without the spoon retractor as needed. When you get to the end, you pull the fish out and close the incision by tightening and tying the continous suture. The rest of the closure is superficial and should not jeopardize the implant.
I suppose you could injure the implant by instrument use inside the pocket if you are working to relieve some tightness, for example, after the implant has been put in, but there are special instruments such as the Tebbetts spatula retractor that can push the implant out of the way to protect it when you do this.
I think the most likely scenario is a needle injury during closure which is an unwelcome surprise to any surgeon, and unless it is a saline implant, may not be apparent until it is detected long after the surgery is completed.

Hello, thank you for your question. So it can certainly occur during surgery. The silicone shell can be pierced by a suture(needle), especially when closing the incision made. The outer shell is thin and we have to be careful, how we handle it especially when using instruments or sutures which can easily puncture or damage the implant.

Sharp instruments, like scissors or pick ups, could damage the covering of the implant, but more damage is often done from needles while sewing up the incision. Most of us have tricks to avoid damaging the implants and keeping sharp things away from the cover.

While there is a planned sequence to any plastic surgeon's breast augmentation, there is always a theoretical risk of implant injury as it is being placed into its breast pocket.
The most likely culprits of implant damage during surgery would be sharp or metallic instruments, such as scissors, skin retraction hooks (which have sharp ends), tissue forceps, and even smooth retractors (such as ribbon retractors, or Army Navy retractors), which is pushed up against an implant with enough force, can induce enough pressure to weaken the integrity of the implant shell, leading to a rupture.
A silicone rupture is not nearly as concerning as it was with older generation implants, as the silicone is much more form stable and cohesive (the way the molecules of silicone bind or cross link to one another). If a rupture were to happen, chances are that a patient would not have symptoms and that the gel would nonetheless stay contained within the implant shell, as implants nowadays are 5th generation with 'gummy' characteristics.
A saline rupture would be evident immediately or over the course of a few days, as saline would leak out the implant, and the appearance of the ruptured side would look as if no implant were placed (i.e., look deflated), while the other side would remain augmented. A bilateral rupture would be highly unlikely from accidental instrumentation during surgery, but it could in theory happen if bad technique were applied equally to both sides.