Symbiosis: Apache PHP7 module isn't enabled automatically following dist-upgrade from Symbiosis Jessie
During the dist-upgrade from Symbiosis Jessie to Stretch, Apache will not enable the PHP7 module as it conflicts with PHP5 (which should already be enabled). The PHP5 module should therefore be explicitly disabled in favour of PHP7.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information