I've always had this problem and it still comes back when I have long periods without practice. What works for me is instead of mentally aiming for the right corner of the serve box, I mentally aim to hit it out. Or aim to hit the right net post. Ends up that I'll miss my target too far to the left, which ends up being "in".
I keep practicing that and I find that the resulting landing spot and my mental target slowly "syncs" closer and closer.