Problem with grep on multiple files and not getting desired output

I am using the below command on a file to extract few lines based on chr# ( different chromosome numbers). This is just a single file am working on. i have 8 such files and for each file I have to do this for chr(1to 22 and then chrX and chrY) , am not using any loop, I did it invidually , but if you see that I want the header to be intact for each of my output. If I execute individually I get the header in the output but if am running but if I run the script for all the 8 files together which is like 8*24 commands in a script one after another, the output does not have any header. Can you tell me why is this happening? Help would be appreciated

more S_313_IPS_S7995.coverage.sample_interval_summary | head -n1; more S_313_IPS_S7995.coverage.sample_interval_summary | grep "chr1" > S_313_IPS_S7995.chr1.coverage
more S_313_IPS_S7995.coverage.sample_interval_summary | head -n1; more S_313_IPS_S7995.coverage.sample_interval_summary | grep "chr2" > S_313_IPS_S7995.chr2.coverage
more S_313_IPS_S7995.coverage.sample_interval_summary | head -n1; more S_313_IPS_S7995.coverage.sample_interval_summary | grep "chr3" > S_313_IPS_S7995.chr3.coverage
more S_313_IPS_S7995.coverage.sample_interval_summary | head -n1; more S_313_IPS_S7995.coverage.sample_interval_summary | grep "chr4" > S_313_IPS_S7995.chr4.coverage
more S_313_IPS_S7995.coverage.sample_interval_summary | head -n1; more S_313_IPS_S7995.coverage.sample_interval_summary | grep "chr5" > S_313_IPS_S7995.chr5.coverage
more S_313_IPS_S7995.coverage.sample_interval_summary | head -n1; more S_313_IPS_S7995.coverage.sample_interval_summary | grep "chr6" > S_313_IPS_S7995.chr6.coverage
more S_313_IPS_S7995.coverage.sample_interval_summary | head -n1; more S_313_IPS_S7995.coverage.sample_interval_summary | grep "chr7" > S_313_IPS_S7995.chr7.coverage
more S_313_IPS_S7995.coverage.sample_interval_summary | head -n1; more S_313_IPS_S7995.coverage.sample_interval_summary | grep "chr8" > S_313_IPS_S7995.chr8.coverage
more S_313_IPS_S7995.coverage.sample_interval_summary | head -n1; more S_313_IPS_S7995.coverage.sample_interval_summary | grep "chr9" > S_313_IPS_S7995.chr9.coverage