Fix 404 JS/CSS issues by recompiling the static content

Check which language the 404 URL contains. For instance:

adminhtml/Magento/backend/nl_NL/images/magento-logo.svg

if en_EN works:

adminhtml/Magento/backend/en_EN/images/magento-logo.svg

Then you have to compile static content for NL language. Use -vv for extra verbose

php7.0 bin/magento setup:static-content:deploy nl_NL -vv