Below verify error was captured by a mongo validateCollection test run, indicating the associated history store key was not found in the data store file.  

WT_SESSION.verify: __verify_history_store_id, 1296: the associated history store key \\94 was not found in the data store file:collection-29-8843939404790402723.wt: WT_PANIC: WiredTiger library panic"

It could be related to the recent HS verification re-architecture change addressed in WT-5911.