The message is caused by Safari’s incompatibility with the gzip compression sent by the web server in response. If you still have the problem after deactivating the cache plugin you are using, it could also be related to cookies that Safari processed incorrectly in this context.
Therefore, deactivate the cache plugin again and then delete all cookies that your Safari has saved for your site. If it works after that, it’s related to the compression that the cache plugin uses. If it still doesn’t work after that, it could also be the hosting. Contact your hoster for this.