Hi,
I enabled PHP Error reporting (and wp_debug in wp-config.php), and I see with a standard demo import the follwing php error notices, when I open a product page.
Notice: Undefined offset: 0 in /home/public_html/wp-content/plugins/js_composer/include/classes/core/class-vc-base.php on line 447
Notice: Trying to get property 'ID' of non-object in /home//public_html/wp-content/plugins/js_composer/include/classes/core/class-vc-base.php on line 447
Notice: Undefined offset: 0 in /home/public_html/wp-content/plugins/js_composer/include/classes/core/class-vc-base.php on line 483
Notice: Trying to get property 'ID' of non-object in /home/public_html/wp-content/plugins/js_composer/include/classes/core/class-vc-base.php on line 483