We have the problems with our WordPress site on IIS 8.5 server with PHP 7.0.4 64-bit.
From the WordPress debug log:
[30-May-2016 16:53:23 UTC] PHP Warning: require_once(C:\inetp): failed to open stream: No such file or directory in C:\inetpub\wwwroot\StayVA.com\wp-content\plugins\woocommerce-subscriptions\includes\gateways\paypal\class-wcs-paypal.php on line 22
[30-May-2016 16:53:23 UTC] PHP Fatal error: require_once(): Failed opening required 'includes/class-wcs-paypal-standard-switcher.php' (include_path='.;C:\php\pear') in C:\inetpub\wwwroot\StayVA.com\wp-content\plugins\woocommerce-subscriptions\includes\gateways\paypal\class-wcs-paypal.php on line 22
The site usually works fine but at some (unpredictable) moments this message starts to appear many times continiously and then every request to every page of the site gets 500 error. Only IIS restart helps.
Looking at the line mentioned in the error message, I see no potential problems:
require_once( 'includes/class-wcs-paypal-standard-switcher.php' );
The file exists, of course.
Same errors appear regularly referencing different "not found" files:
[27-May-2016 09:01:12 UTC] PHP Warning: require_once(C:\inetpub\wwwroot\StayVA.com\wp-content\plugins\woocommerce-gateway-authorize-net-cim\lib\skyverge\woocommerce\class-sv-wc-plugin-compatibility): failed to open stream: No such file or
directory in C:\inetpub\wwwroot\StayVA.com\wp-content\plugins\woocommerce-gateway-authorize-net-cim\lib\skyverge\woocommerce\class-sv-wc-plugin.php on line 251
[27-May-2016 09:01:12 UTC] PHP Fatal error: require_once(): Failed opening required 'C:\inetpub\wwwroot\StayVA.com\wp-content\plugins\woocommerce-gateway-authorize-net-cim\lib\skyverge\woocommerce/class-sv-wc-plugin-compatibility.php' (include_path='.;C:\php\pear')
in C:\inetpub\wwwroot\StayVA.com\wp-content\plugins\woocommerce-gateway-authorize-net-cim\lib\skyverge\woocommerce\class-sv-wc-plugin.php on line 251
[29-May-2016 23:51:31 UTC] PHP Warning: require_once(C:\inetpub\wwwroot\StayVA.com\wp-content\plugins\woocommerce-gateway-authorize-n): failed to open stream: No such file or directory in C:\inetpub\wwwroot\StayVA.com\wp-content\plugins\woocommerce-gateway-authorize-net-cim\lib\skyverge\woocommerce\payment-gateway\class-sv-wc-payment-gateway-plugin.php
on line 205
[29-May-2016 23:51:31 UTC] PHP Fatal error: require_once(): Failed opening required 'C:\inetpub\wwwroot\StayVA.com\wp-content\plugins\woocommerce-gateway-authorize-net-cim\lib\skyverge\woocommerce\payment-gateway/api/interface-sv-wc-payment-gateway-api-payment-notification-credit-card-response.php'
(include_path='.;C:\php\pear') in C:\inetpub\wwwroot\StayVA.com\wp-content\plugins\woocommerce-gateway-authorize-net-cim\lib\skyverge\woocommerce\payment-gateway\class-sv-wc-payment-gateway-plugin.php on line 205
Note that file paths and names are truncated in the log.
Here is phpinfo: http://www.stayva.org/info.php