Goodneighbor warehouse crash while completing 'The Cleaner' quest in Fallout 4?

I've encountered a consistent crash while attempting to clear the Goodneighbor warehouses of Triggermen (Whitechapel Charlie's 'Miscellaneous' quest: The Cleaner).

In one of the warehouses, killing the final Triggerman on the top floor immediately crashes to Desktop - making completing the quest impossible.

Is there a workaround?

There are a couple of small workarounds that may do the trick:

• Disable all other quest markers, only enabling 'The Cleaner' from the Miscellaneous Quests list.
• Don't kill the final Triggerman with VATS, use manual aiming or explosives instead.
• Tell a companion to move to the top floor and have them kill the final Triggerman.

This thread on the Steam Community discusses the bug and provided inspiration for this answer, however nothing here is a definitive fix: you may get away with only enabling the quest, or you might try each step and the game may still crash.

In my case, enabling the quest and having my companion get the final kill (while I wasn't watching) was the only way to get past it - manually aiming, using explosives etc still crashed the game for me.

I believe the bug may be caused by some errant interaction between the Quest and XP award systems, so not being awarded XP for the kill avoided the problem for me.