Graph API Legend incorrect data

I get the graphics of the API and I retrieve legends with inconsistent and different data from the original. You can see via the 2 screenshot attached.


My install is not up to date :

Version 1.36 - Sat Jan 27 2018 13:57:40 GMT+0100
DB Schema #232
Web Server Apache/2.4.18 (Ubuntu)
PHP 7.0.22-0ubuntu0.16.04.1
MySQL 10.0.31-MariaDB-0ubuntu0.16.04.2
RRDtool 1.5.5

Every time I get multiple graph, only the first is correct and the others have corrupted data.