the only problem
That wasn't the only problem.
El único problema que tenemos ahora es que alguien aquí te echa de menos.
The only problem we have now is that someone here misses you.
— Ofrenda a la tormenta (2020)
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 de 1900 (1998)
El único problema es conseguir una llave.
The only problem is getting a key.
— Buenos Muchachos (1990)
That’s not the only problem.
Este no era el único problema.
This was not the only problem.
It wasn't the only problem.