For Cesc, use him as your playmaker and give him a free role, creative freedom of 15-18, attacking mentality or 11-13, mixed forward runs, mixed run with ball, often long shots, often thru balls, mixed crossing...
There's no bug, you just have to pay close attention to your tactics... if he's playing poor it could be one of many reasons, but the most common is it's too cramped in midield, so spread your width more and free up space, he's not finding any players free to pass to, so have a look at their postition/mentality and tweak slightly, or he could just be having an off day...
Have you read the Tactical Theorems & Frameworks?