Can a second hair transplant in the crown cause shock loss of the transplanted hair that was transplanted in the first FUE?

Dear Mike, Nothing to worry. Usually it is not possible to have shock loss of previously transplanted hair. Kindly meet an expert. 

Shock loss is a transient stage of hair dropping after a hair transplant operation, and it is estimated to be a passing condition. It is the effect of trauma to the scalp which occurs due to several reasons.
Most of the time, it is fleeting and re-growth of strands are seen after a specific period. Shock loss can transpire during any variety of hair transplant techniques. After all hair transplant surgeries are performed, grafts encompassing the recipient area may endure trauma, and as a consequence of which they fall out.
There are two types of shock loss after a hair transplant:
Temporary shock loss
Temporary Shock loss is an effect of trauma to the scalp and it occurs due to several reasons. The main feature of temporary shock loss is that the hair regrows after a particular period, regardless of the cause. It’s essential to know, during a hair transplant, once the graft is embedded into the recipient region, it can potentially harm the surrounding follicles.
Permanent shock loss
Permanent Shock Loss is the outcome of a sustained trauma to the hair follicle that does not benefit to correctly regrow hair. Typically, these hairs are already being transformed by dihydrotestosterone (DHT), which is the accountable hormone for inducing hair loss and baldness, and which will be permanently lost in some years. Permanent Shock Loss happens when the hair has been injured during the method of transplantation.
Can you forestall hair loss after a hair transplant?
There are no solutions set in stone, which can prevent hair shock loss after or during a transplant. Nevertheless, few preventative ways can be implemented to reduce the amount of hair loss.
Medication:
Some specialists may prescribe medications like; minoxidil or rogaine to reduce the amount of hair fall, which happens during/after hair refurbishment surgery. The physician may also prescribe Finasteride, a DHT blocker through the recovery process, to depreciate hair shock and fallout.
Enhancing the graft density:
When the scalp is stressed or seems bewildered, the hair follicles enter the dormant phase to soothe themselves. Yet, grafts falling out after a hair transplant is not entirely preventable. If the specialist maximizes the number of grafts without harming the surrounding follicles, then the risks of shock hair fall can be lessened.
Decreasing trans-section risk:
Trans-section occurs when the internal structures of the hair follicles are critically damaged through the transplant procedure, to a position where they can’t be restored. This is serious because it can end in permanent shock hair loss. Even though this situation is quite rare, the most reliable way to prevent this is by looking for a qualified and expert surgeon.
Also, if the surgeon transplants the grafts too closely or makes the channels too big, as a consequence, the neighboring natural hair may fall after the surgery. All these are reasons why choosing the most suitable clinic for a hair transplant is evermore justified to achieve good results. Let's not neglect that we are talking about aesthetic surgery, so it necessitates experience and accuracy to provide the patient their desired look.

It might happen to the existing transplanted hairs if the second one does not follow the angle or direction, hopefully they will grow back 3-4 months after procedure.