Learn Farsi: هنگام دویدن هنرورها، دوربین شکست.

Hengâm literally translates to "time" or "moment," but here it functions as the preposition "during." Because it behaves grammatically like a noun modifying the action that follows it, it requires an ezâfe to link it to the verbal noun davidan (running), becoming hengâm-e davidan.

Could we say this using a conjugated verb instead of the infinitive davidan?

Yes. Using the infinitive davidan (running) as a verbal noun is a concise, slightly formal way to show simultaneous action. You could alternatively use a full subordinate clause with ke (that): hengâm-i ke honarvar-hâ mi-davidand (at the time that the extras were running). Notice that when you add ke, hengâm takes the indefinite -i suffix instead of an ezâfe.

I know honar means "art", so why does honarvar-hâ translate to "extras"?

While honarvar literally means "art-possessor" (combining honar with the suffix -var), in the context of film and television, it is the standard industry term for a background actor or "extra." Here, it is linked to the action with a second ezâfe, creating the chain hengâm-e davidan-e honarvar-hâ (the time of the running of the extras).

The verb shekast can mean "he/she broke [something]". How do we know it means "the camera broke" here?

The verb shekastan (to break) can be both transitive (taking a direct object) and intransitive (happening on its own), just like the English word "break." Because there is no object marker on and no other subject in the second clause, acts as the subject of the intransitive verb. Therefore, it translates to "the camera broke."