since JIRA is emptying the value of active sprint, but not emitting this information via webhook, aha retains last active sprint in active sprint field. Which is cool as this actually enables creating a pivot report that would show backlog items delivered per sprint. ( "sprint" field can't be used as it may contain many sprints).
Unfortunately this unintended benefit disappears when you update all records (button in aha integration config). As what it does to active sprint field (used in pivot report described above as "last active sprint"), is that updates its value to empty for all backlog items that were delivered in closed sprints.
There is currently no alternative to avoiding this issue but to temporarily reconfigure the integration in aha to prevent syncing active sprint field when pushing "update all records". Which is not a full solution as it does not capture the set of items that were closed items and their lasts active sprints were closed in synchronization gap.