Unknown error not able to understand - wkhtmltoimage exited with non-zero code -9. error:

[ABHISHEK-KEDAR-21]

File "/home/frappe/docker-bench/env/lib/python3.8/site-packages/imgkit/api.py", line 90, in from_string
return rtn.to_img(output_path)
File "/home/frappe/docker-bench/env/lib/python3.8/site-packages/imgkit/imgkit.py", line 246, in to_img
raise IOError("wkhtmltoimage exited with non-zero code {0}. error:\n{1}\n\n{2}".format(exit_code, stderr, xvfb_error))
OSError: wkhtmltoimage exited with non-zero code -9. error:
Loading page (1/2)
[> ] 0%
[======> ] 10%
[=========> ] 16%
Warning: Failed to load file:///assets/frappe/css/bootstrap.css (ignore)
Warning: Failed to load file:///assets/frappe/css/font-awesome.css (ignore)
[=========> ] 16%
[============> ] 20%
[=============> ] 23%
[===============> ] 25%
[================> ] 28%
Warning: Failed to load /files/Limit_Sale.PNG (ignore)
[=================> ] 29%
[===================> ] 32%
Warning: Failed to load /files/pohaa759c5.jpg (ignore)
[===================> ] 33%
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Warning: Failed to load /files/Oral-B-Shiny-Clean-Med-12+1-@-20.jpg (ignore)
[========================> ] 41%
[=========================> ] 43%
[===========================> ] 45%
[===========================> ] 46%
[=============================> ] 49%
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Warning: Failed to load /files/Godrej-No1-Sandal-3+1-64.jpg (ignore)
[==============================================> ] 78%
Warning: Failed to load /files/Patanjali-Shampoo-Aloevera-1 2019-04-15 19:17:49.jpg (ignore)
Warning: Failed to load /files/Delivery_Beat_Route_2 2019-05-19 00:45:01.PNG (ignore)
[===============================================> ] 79%
Warning: Failed to load /files/Untitled_2.png (ignore)
[===============================================> ] 79%
Warning: Failed to load /files/Godrej-No1-Lime-3+1-64.jpg (ignore)
[================================================> ] 81%
[=================================================> ] 82%
Warning: Failed to load /files/Superia-Naturals-Lemon-and-mint-3+1-@30.jpg (ignore)
[=================================================> ] 83%
Warning: Failed to load /files/Superia-Naturals-Neem-and-coconut-3+1-@30.jpg (ignore)
[===================================================> ] 85%
[===================================================> ] 86%
[====================================================> ] 87%
[====================================================> ] 88%
Warning: Failed to load /files/Bundle_test.png (ignore)
[====================================================> ] 88%
[====================================================> ] 88%
[=====================================================> ] 89%
[=====================================================> ] 89%
Warning: Failed to load /files/Mortein_PG_8h_Coil_+_ActivCard_Free.png (ignore)
[=====================================================> ] 89%
[======================================================> ] 90%
[======================================================> ] 90%
Warning: Failed to load /files/Delivery_Beat_Route_1 2019-05-07 12:50:25.PNG (ignore)
[======================================================> ] 90%
[======================================================> ] 90%
[============================================================] 100%
Rendering (2/2)
[> ] 0%
[===============> ] 25%

Anyone please help me with this.
Used these options:

        options = {

            'quality': quality,
            'width': width,  
            'enable-javascript': None,
            'enable-local-file-access': None,
            'images': None,
            'no-stop-slow-scripts': None,
            # 'enable-smart-width': None,
            'enable-plugins': None,
            'encoding': 'UTF-8',
            'disable-smart-width': None,
            'load-media-error-handling':'ignore',
            'load-error-handling':'ignore'
        }