python3 script runs on startup using (crontab -e ) for sometime and after that it automatically stops. why?

Question

i am using Raspberry Pi 3 to run a python3 script which runs VLC player to display images and videos, it run smoothly and continuousl when i run manually in the terminal like sudo python3 /home/pi/main.py >> /home/pi/logg.txt

but when i run it on startup on crontab -e like @reboot sudo python3 /home/pi/main.py >> /home/pi/logg.txt 2>&1

it runs for some time and then it stops running automatically. I don't know what is happening?

and both time it create same log like

gles2 generic error: parent window not available
[676fd628] mmal_xsplitter vout display error: Failed to open Xsplitter:opengles2 module
[6a32d3a8] xcb generic error: window not available
[676fd628] mmal_xsplitter vout display error: Failed to open Xsplitter:xcb_x11 module
[6a318640] gles2 generic error: parent window not available
[6a351510] mmal_xsplitter vout display error: Failed to open Xsplitter:opengles2 module
[6a318640] xcb generic error: window not available

Any help?