Schockloss is a temporary or permanent loss of original hairs due to its implantation. This occurs only when placing grafts in an area where there are original hair. Schockloss is unpredictable and can therefore in principle always occur.

Temporary shock loss: part of the original hairs fall out after transplantation, often associated with hair transplantation. After 3-6 months, both the original and hair transplants regrow.
Permanent schockloss: part of the original hair fall out after transplantation, often associated with hair transplantation. The original hair, or a part of it will not grow back. The reason is that these schockloss hairs were already very weak and wouldn't grow  much longer anyway.
Tip: If possible start taking finasteride at least 6 months prior to hair transplantation. This way the original hairs strengthen and there is less chance of schockloss.