Learn Spanish (Latin America): Bajaron el andamio de repente y solté la polea. - They lowered the scaffold suddenly and I let go of the pulley.

You would say por poco y suelto la polea. Even though the trigger action is in the past tense (bajaron), the phrase por poco y is traditionally followed by the present indicative to vividly describe a past event that almost happened but was averted.

Could solté also translate to 'I dropped'?

Yes, the verb soltar means to release or let go of, which often results in dropping something. However, if you want to emphasize that it was an accident (it slipped from your hands), a Spanish speaker would be more likely to use the accidental construction se me cayó la polea.

Why are both verbs (bajaron and solté) in the preterite rather than the imperfect?

Both verbs represent sudden, completed actions in a chain of events. The phrase de repente (suddenly) highlights that the lowering of the scaffold was a single, abrupt event that interrupted the timeline, which immediately triggered your reaction to let go of the pulley.

Does bajaron imply a specific group of people lowered the scaffold?

It might, if specific workers were already mentioned. However, Spanish frequently uses the third-person plural (bajaron) as an impersonal statement when the identity of the people doing the action isn't important. It functions similarly to the English passive voice: 'The scaffold was lowered.'