I have a Statamic site that's been deployed to an Azure instance. I'm not in control of the instance, so I've been trying to work with the person in control to resolve an error we're seeing. Whenever we try to update content in the control panel, we get the following error message:

There was an issue saving your data. More detail can be found in your logs.

However, no error log is being generated. I'm unable to update Statamic as well. My gut tells me it's an issue with folder permissions, but those seem to work differently on Azure, and not having access to the instance has made it difficult to try to solve the issue. There's only one error showing up in the php error log:

PHP Warning: require(/home/site/wwwroot/statamic/bootstrap/../vendor/autoload.php): failed to open stream: No such file or directory in /home/site/wwwroot/statamic/bootstrap/autoload.php on line 17 [24-Jan-2019 19:02:57 UTC] PHP Fatal error: require(): Failed opening required '/home/site/wwwroot/statamic/bootstrap/../vendor/autoload.php' (include_path='.:/usr/local/lib/php') in /home/site/wwwroot/statamic/bootstrap/autoload.php on line 17 [24-Jan-2019 19:03:39 UTC] PHP Warning: require(/home/site/wwwroot/statamic/vendor/composer/../symfony/polyfill-mbstring/bootstrap.php): failed to open stream: No such file or directory in /home/site/wwwroot/statamic/vendor/composer/autoload_real.php on line 66 [24-Jan-2019 19:03:39 UTC] PHP Fatal error: require(): Failed opening required '/home/site/wwwroot/statamic/vendor/composer/../symfony/polyfill-mbstring/bootstrap.php' (include_path='.:/usr/local/lib/php') in /home/site/wwwroot/statamic/vendor/composer/autoload_real.php on line 66

I'm not sure if it's related to the issue we're having, but it's the only error showing up. We're using PHP 7.2 and Statamic 2.11.9. Do you have any suggestions on what the root issue might be?