server error 500 for some product pages

[ Moderator note: Topic decapped. Please do not use all caps again, it is considered to be rude. ]

Any suggestions are much appreciated!

We use composite products and this problem has happened 2 times now. First time around we just put a backup back, but now it’s happened again. Everything worked fine first and then suddenly we lose some product-pages after a few days. We have 3 composite products and when you filter on the category in the backend it shows you there are 3, but none show up in the list. 1 of those does shows up in the shop on the website and can be configured, the other 2 don’t show at all and you just see a white background. The console tells me there is a server error 500 and the server log shows me the bit below. Everything points to the normal woocommerce plugin, but I have no idea how to read this. FYI, we cloned the site after first time we restored it and the clone is still working fine. As it seems to be a bit random I’d love to find out what causes this and how I resolve it.


[Wed Oct 26 13:21:28.391533 2016] [lsapi:error] [pid 698171:tid 140145875437312] [client 183.89.0.73:52904] [host gamepcdirect.nl] Backend fatal error: PHP Fatal error: Uncaught Error: Call to a member function is_downloadable() on boolean in /home/u7307p4960/domains/gamepcdirect.nl/public_html/wp-content/plugins/woocommerce/includes/wc-template-functions.php:701\nStack trace:\n#0 /home/u7307p4960/domains/gamepcdirect.nl/public_html/wp-content/themes/porto/woocommerce/content-single-product.php(37): woocommerce_get_product_schema()\n#1 /home/u7307p4960/domains/gamepcdirect.nl/public_html/wp-includes/template.php(574): require('/home/u7307p496...')\n#2 /home/u7307p4960/domains/gamepcdirect.nl/public_html/wp-content/plugins/woocommerce/includes/wc-core-functions.php(173): load_template('/home/u7307p496...', false)\n#3 /home/u7307p4960/domains/gamepcdirect.nl/public_html/wp-content/plugins/woocommerce/templates/single-product.php(37): wc_get_template_part('content', 'single-product')\n#4 /home/u7307p4960/domains/gamepcdirect.nl/public_html/wp-includes/template-loader.php(75): include('/home/u7307p496...')\n#5 /home/u7307p4960/domains/gamepcdirect.nl/public_html/wp-blog-header.php(19): in /home/u7307p4960/domains/gamepcdirect.nl/public_html/wp-content/plugins/woocommerce/includes/wc-template-functions.php on line 701\n