Here I provide you solution for this issue based on my experience. you can also try this way.
use as a reference to blew mail.

Dear Team Amazon,

I have already raised many cases for the same complains since last year. I was not getting many of my return parcels from local ATS. Some of them I never get, so I filed complain at local ATS authorities about this on Saturday, 2nd Sept, 2017. I also raised this issue with amazon on Monday, 04 Sept, 2017 in the morning with Case ID 3914876862.

After the strict complain to local ATS and Amazon, courier team returned me 25 parcels of returns together on Monday afternoon. 20 out of 25 parcels were damaged by someone, most probably by someone from local courier team.

On our research, we found that, to solve our complains about missing parcels, they printed new labels of missing parcels. Opened our currently available parcels, took some items from the combo of multiple items and arranged total 20 parcels. In this 20 parcels, we sent total 41 items as single item, combo of two, three and five items. But in return, we got only 14 items in 14 parcels and 6 wrong products in 6 parcels.

I again and immediately informed ATS authorities about missing items and damaged parcels. 6-7 persons from ATS local team came at my office, checked and verified that parcels are actually damaged and items are missing. They also took photographs of all parcels and told me to file SAFE-T claim for these parcels.

But I believe that SAFE-T claim isn’t solution for this problem. I told local ATS authority and amaozn many times to research why the parcels are getting damaged and items getting missing and find who is responsible for this.

Today again I am going to raise this issue with 20 order IDs which are affected, listed as below.

Order ID Reverse tracking ID
408-8359531-0874707 611155826416
404-2627455-9473128 611153891195
407-4361291-1533100 610188005690
408-7699826-4629132 611153932799
407-1156998-6377128 610188598062
405-8116224-7053109 610188351292
171-4903128-7727526 610187711868
404-8253858-0519501 611154420813
171-0289535-9363551 611153876536
406-6998689-8297155 611154602516
403-3948038-9336356 611154026190
408-9080896-2000360 611153876536
408-4781618-2631504 610187804898
403-1378679-3672315 611155571071
408-3352138-9652310 611155952801
403-6299163-6782715 610187697049
402-6188569-6596333 611155600436
403-4126104-2314712 611154545417
405-4061502-6605950 610188444529
407-6789403-3137941 611154387833

For detailed information, I have attached an excel sheet which includes Order ID, Reverse tracking ID, SELLER PRODUCT ASIN, RETURN TYPE, ORDER Amount, All required images (image links) and all other details.

Parcels shows “Returned to seller” when tracking, but we never get them at our place. I have also sent mail to notice@amazon.in and SAFE-T-Claims@amazon.com for same issue of missing parcels in past.

Below is the list of case IDs which I generated in past for the same issue of related missing parcels and items.

05-Sep-17 Case ID: 3914876862 Complain about Regularly Missing Parcels
25-Aug-17 Case ID: 3886615382 status shows return but not received at seller place
03-Aug-17 Case ID: 3826635192 status shows return but not received at seller place
16-Jun-17 Case ID: 1882623312 status shows return but not received at seller place
19-Oct-16 Case ID: 1631580362 status shows return but not received at seller place
10-jun-16 CASE ID: 1519340942 status shows return but not received at seller place
12-May-16 Case ID: 1497123912 status shows return but not received at seller place
11-May-16 Case ID: 1496448702 status shows return but not received at seller place
09-May-16 Case ID: 1494480542 status shows return but not received at seller place

Because of this problem, As seller we are facing many loses.

Please research this issue and do needful.