the only problem
El único problema es conseguir una llave.
The only problem is getting a key.
— Uno de los nuestros (1990)
Este no era el único problema.
This was not the only problem.
That’s not the only problem.
El único problema era que para todo el mundo, él ni siquiera existía.
The only problem was that, to everyone else, he didn't even exist.
— La leyenda del pianista en el océano (1998)
It wasn't the only problem.
That wasn't the only problem.