"The doctor had accidentally dropped the scalpel."
Translation:bong Haqtaj chaghpu' Qel.
The absence of bong does not mean that the subject was trying to accomplish the action. Haqtaj chaghpu' Qel means simply that "the doctor had dropped the scalpel" and makes no mention of it being accidental or intentional. With the -ta' suffix, it says that "the doctor had accomplished dropping the scalpel," so there is some intentionality included as well as the information that he did in fact accomplish what he was trying to do (dropping the scalpel?).
I don't know how chIch and -ta' interact. Maybe it's as you say, and chIch gets emphasized. Maybe it just sounds redundant. I think of -ta' as perfective with a connotation of intentionality, rather than intentionality with a connotation of perfective, so I think that adding "intentionally" to an English translation of plain -ta' is overtranslating.