How can I solve that orange line problem?
Shellfish,
I am going to make a guess here. I remember seeing some posts in the past regarding a white outline. I believe it had something to do with an alpha over node and premultiply. Search the support forums for premultiply.
Best of Luck!
can’t find it. the only one i found is about the back lighting
It would probably help if you posted a screenshot of your node setup. then I could imaginge it better. 
Try using a dialate/erode node before your alpha over and eroding the map by 1. (value = -1). or so.
I hope that helps!
Murphy
I did not use any node setup