Transplanted hair fall started after 10 months. Is this normal?

You you describe is not normal.  Something is wrong or you have an undiagnosed medical condition.  You need to see your doctor for a recheck.

Many factors could lead to what you have described; too many to discuss in this manner.  Your best option is to speak with your surgeon about your concerns.  Best

I agree this is not typical after a hair transpantation.  Check in with your operating surgeon.  Good luck!

This is not common. You'll want to see your surgeon for an up close examination and possibly a small scalp biopsy.  

Shock loss or acceleration of the normal hair loss pattern occurs after a hair transplant. This can be prevented with the drug finasteride (see video below). 

It is not normal to lose the transplanted hair at a very high rate and at the same time.  However if your doctor harvested the grafts outside of the donor zone which is in the back of your head this is a very common result.

What you are describing is consistent with alopecia areata (aa). I recommend you seeing a dermatologist well versed in aa. In some forms of aa, there can be shedding of the posterior scalp (ophiasis).  I would quickly seek treatment with a hair specialist dermatologist and treat this shedding.