ERR_CONTENT_DECODING_FAILED for one file after Joomla update

Question

After updating Joomla to 3.8.1 today most of the admin tabbing and navigation functions stopped working in Chrome, FireFox, Win Safari, and IE 11. media/jui/js/bootstrap.min.js was failing to load with ERR_CONTENT_DECODING_FAILED. It still works in MS Edge.

This is occurring on machines in multiple locations and over multiple ISPs.

Actions taken (none of which have resolved):

1. Deleted file from server and replaced with backed up copy from last week and re-issued chmod 0644
2. Verified that public $gzip = '0'; in configuration.php
3. Tested in MS Edge where the error did not occur
4. Used MS Edge to go to Joomla Global Configuration > Server Settings and set Gzip Page Compression to No. Had been Yes.
5. Found that in browsers where it was failing if JS file is accessed without the versioning query string the browser can load file without error.
6. Found in Safari, IE 11, and iPhone Chrome the JS file displays and appears to be gzipped or otherwise encoded. Screenshot:
7. Cleared browser cache in Chrome
8. Went to chrome://net-internals and clicked Flush Socket Pools and Close Idle Sockets
9. Cache settings checked and it has been set to off the whole time:

10. System - Page Cache module also disabled

Answer 1

In this case the client had failed to mention they had added Sucuri Firewall service and that was where they corrupted cached file was being delivered from. Cleared cache at Sucuri and file no longer throws ERR_CONTENT_DECODING_FAILED