Address pointed to by loc_block changed (by system)

I have some event templates using loc_block to define event locations. There are 2 main templates with 2 different locations. One address in civicrm_address pointed to by the loc_block_id in one template has been updated/changed (street_address, city) but not sure how - any clues would be appreciated (needless to say, I didn't change the address myself in the Manage Events functions).