When using RewriteRule ….[P] with mod_gzip there are often problems
To resolve this add the following directive to mod_gzip

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mod_gzip_item_include handler proxy-server
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mod_gzip_item_include mime "application/x-httpd-php.*"
mod_gzip_item_include mime httpd/unix-directory
mod_gzip_item_include handler ^server-status$

mod_gzip_item_exclude file \.css$
mod_gzip_item_exclude file \.js$

mod_gzip_item_exclude reqheader "Via:.*1\.0 PROXY"
mod_gzip_item_exclude reqheader "Via:.*1\.0 lavoisier \(NetCache NetApp\/5\.0\.1R2\)"