Lock not always released if browser closed in edit mode.

We have had a few instances in the last couple weeks (since deployment of an I.P. application) where a user has either closed the browser while in edit mode, or received some sort of error when saving plan data and the browser closed, where the Lock in RSPLSE/SM12 was not deleted. In the last case, the lock stayed for 6 hours before we were notified to manually delete the lock. The user had closed all windows, even restarted her machine.

Any insight on how to enforce removal of locks if browser is closed? We are on SAPKW70017 and BI Java Support Package Patch SP015