I have faced the same issue and its like the system was throwing the below error

Magento ver. 2.2.0-dev – A technical problem with the server created an error. Try again to continue what you were doing. If the problem persists, try again later

To fix the issue I have deployed the static content again and done reindexing and cache clearing

php bin/magento setup:static-content:deploy

php bin/magento indexer:reindex

php bin/magento cache:flush