What are the known risks of minimally invasive surgery?

Which one? Minimally invasive surgery(mis)includes a wide variety of operations performed by many different types of surgeons. The risks of any operation are very dependent on the organ being operated on and the health of the prospective patient. As a general surgeon, mis is used synonymously with laparoscopic surgery, placing a small camera in the abdomen and working thru keyhole-sized incisions.
Depends. Minimally invasive surgery of the spine has less skin, muscle and bone damage and blood loss, quicker recovery and less need for pain medicine, but there are still surgical risks from general anesthetic, nerve damage, infection, bleeding, spinal fluid leaks, instability, but many surgeons think these risks are less.
Varies. The term minimally invasive surgery is a broad term that describes doing a surgery with similar surgical goals as a traditional surgery, but in a less invasive fashion. The term has been used across most surgical specialties and so the risks are individualized to the specific surgery involved. You would certainly want to ask your surgeon about the possible risks and benefits of your case.
Depends on doctor. Minimally invasive surgery has an earlier recovery when performed by experienced surgeons who specialize in these types of procedures. When they are performed by inexperienced surgeons or those who use equipment where visualization is difficult, there can be increased risk of injury to nearby structures. These particular risks depend on the minimally invasive procedure performed.