Issue proxy:error AH00898: Max-Forwards value 'helper.magius.it' could not be parsed

[Azurel]

I get often this errors in log

[proxy:error] [pid 29093] [client xxxx:55234] AH00898: Max-Forwards value 'helper.magius.it' could not be parsed returned by /index.php, referer: xxxx

CentOS Linux 7.3.1611 (Core)‬
Product Plesk Onyx Version 17.0.17 Update #18
Server version: Apache/2.4.6 (CentOS) built: Nov 14 2016 18:04:44

What can I do to fix this?