/bin/sh: ntpq: command not found

I've got this strange behaviour Empty string parsing ntpq command result, but let me resume and refocus the problem:

I'm executing a java program launched using a shell script that goes like this:

#!/bin/bash export PATH=.:$PATH java -jar myJar.jar & 

Inside my java code I execute this piped command

ntpq -c peers | awk ' $0 ~ /^\*/ {print $9}' 

in order to obtain the offset of the NTP synchronized server.

To execute a piped command inside a java program, I've to use the above mentioned line as an argument of /bin/sh. I execute /bin/sh not the piped command directly.

This is the equivalent that you can launch in a console 1

/bin/sh -c 'ntpq -c peers | awk '"'"' $0 ~ /^\*/ {print $9}'"'"'' 

Example output from ntpq

 remote refid st t when poll reach delay offset jitter ============================================================================== *172.30.100.1 172.22.204.171 4 u 207 1024 377 1.490 53.388 49.372 

Parsing it with awk, I obtain

53.388 

Usually it goes well, but sometimes for reasons unknown [This is my question] my program stops working fine. It returns nothing when the execution of the piped command from the console returns a number.

Recovering the err from the executed process created by java, I've obtained this text

/bin/sh: ntpq: command not found

So, sometimes I can execute 1 from a java program and sometimes I can't. Something is happening in the SO behind the scene. Can someone enlighten me, please?