When user open a parent case and acquire a lock on it.
Then same user acquires a lock on child case as well and resolve the child case.
Once the user resolved the child case, "Resolve" OOTB activity will try to update the parent case pxCoveredCountOpen and set the ticket "AllCoveredResolved".
When the parent case is still in lock it holds old value of pxCoveredCountOpen (workpage) and user process the case it parent case will commit with the current work page properties (rollback the pxCoveredCountOpen set by child case).
***Edited by Moderator Rupashree to update Capability tags***