Problem with tooltip, multi value don't work anymore

Hi all, 

I need your help with a problem I didn't have before.

I created a tooltip with multiple values for a same display name, it worked before without any problem and now it's not working. I checked with my old code version and it's still not working...

My chart should show me (it's the data I use for my point) : 

And it only shows me :

What is the reason for this change ? Has there any tooltips-related changes in an update recently ? 

Thank you !

EDIT: It seems to be related to the fact that my two last arrays have the same display name, but it wasn't a problem before, so what has change ?