We don't have any cause information,
but the entrance to Guayanilla harbor is very difficult.
In one sample of 48 "offshore" groundings from a USCG database,
11 of them were just outside Guayanilla,
a relatively same port in terms of throughput.
This was probably a navigation error,
possibly a conning error,
quite possibly abetted by poor vessel manueverability.
But with the information we have we just can't say.
For now the CTX cause is blank.
This ship had a bad engine room fire in 1955
in the Persian Gulf.