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When enabling the Cache plugin in Joomla 3.x it might report the error ERR_CONTENT_DECODING_FAILED and stop rendering pages.
The problem seems to be that the Cache plugin does not properly support GZIP compression - even if it's enabled by the server and enabled within .htaccess as described in this KB.
For now it seems as if there's only 1 solution to this: Disable GZIP-Compression:
In case you cannot access the websites' backend anymore you can find this setting within the file /configuration.php. The option in this file can be set as following:
public $gzip = '0';