Two too strong personalities to really work together in the long time, and Stalin cannot purge him as he is too distant and the red army is not in Yugoslavia...a thing that a paranoid like Uncle Joe find really upsetting
The two of them basically despised each other, Stalin was already trying to have Tito killed during the war. The best PoD I can think of to prevent a Yugo-Soviet split would be Stalin dying in '46 or '47, and then with someone more pragmatic and less paranoid taking charge
The problem is the leadership of the GDR, which consisted out of VERY LOYAL German communists who escaped to the USSR and were sent back as soon as the war was over to set up an ideal Soviet satellite (the "Gruppe Ulbricht", Ulbricht Group). You'd need to get rid of those guys and still have a large enough KPD, because it wasn't successfull in the first place (hence the forced unification of the SPD and the KPD to the SED, since Stalin feared loosing East Germany to the evil Social Democrats)