R help - Oct 2016 - ERROR : unable to start device PNG on server

Hi

I realize that this question has been asked earlier also, but my problem is
slightly different.
I am running a rscript which runs for multiple datasets in loop and
generates png for every file in the loop. When I run this only local
machine (mac) it runs fine, just that that it takes very long to finish. I
am running it on server, it runs fine till some files but then starts
throwing the following error:

ERROR : unable to start device PNG

before firing the rscript when I check the status for capabilities it gives
me following:
> capabilities()
       jpeg         png        tiff       tcltk         X11        aqua
      FALSE        TRUE       FALSE        TRUE        TRUE       FALSE
   http/ftp     sockets      libxml        fifo      cledit       iconv
       TRUE        TRUE        TRUE        TRUE        TRUE        TRUE
        NLS     profmem       cairo         ICU long.double     libcurl
       TRUE       FALSE       FALSE       FALSE        TRUE        TRUE

When I run it and it terminates giving above error, then the capabilities()
gives following:

> capabilities()
       jpeg         png        tiff       tcltk         X11        aqua
      FALSE       FALSE       FALSE        TRUE       FALSE       FALSE
   http/ftp     sockets      libxml        fifo      cledit       iconv
       TRUE        TRUE        TRUE        TRUE        TRUE        TRUE
        NLS     profmem       cairo         ICU long.double     libcurl
       TRUE       FALSE       FALSE       FALSE        TRUE        TRUE

Note that png and X11 are turned FALSE once it terminates.

Why does this happen automatically? How can I rescue this?
For information, I am using R version 3.3.1 (2016-06-21).

-- 
Anchal Sharma, PhD
Postdoctoral Fellow
195, Little Albany street,
Cancer Institute of New Jersey
Rutgers University
NJ-08901

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