"TEM SIDO" VS. " FOI"

When there is no adverb of time in the sentence, the perfect tense usually translates
‘has/have been’, while the preterite translates ‘was/were’, referring to a single instance in
the past., for example:

Eles têm sido muito compreensivos comigo.
They’ve been very understanding with me.

Eles foram muito compreensivos comigo.
They were very understanding with me.

Ref.: Modern Brazilian Portuguese Grammar - A Practical Guide.