It was the issue in my third party module, after disable the modules, and running commands, my issue was fixed.
The commands which I run after disabling module was:
php bin/magento setup:upgrade
php bin/magento setup:di:compile
php bin/magento setup:static-content:deploy -f
php bin/magento cache:flush
Recently had a very similar issue with a Magento 2 site. Managed to track down the issue to a very important .htaccess file missing in the pub/static folder on the server.
It's unclear how this file was mysteriously removed but re-adding this file from a clean Magento 2 installation rectified the issue.