I know many have had issues of different kind using music production software on El-Capitan. Have read one calling it El Crapitan. But i actualy don't know. I thought things had been fixed. But perhaps not everything it seems.
I guess you have all your things updated. Else you can try that.
Also in the last couple of years i've been hearing about many different issues with Ableton. Perhaps it's hard for software developers to keep up if OS's and DAW's get many changes that affect the plug-ins way to behave.
There are reports with issues using different Operation systems and DAW's.
I don't have any red light. I guess it most be something in your DAW, and that it's indicating some kind of activity is going on.
I understand Arturia follow this forum. However to be sure it's perhaps best if you contact Arturia support about this, and give them all the informations.