in lib/max/Delivery/log.php, line 123:
I didn't fix it myself as it seems it would be using some "untested" code (tracker.php line 220):
// Haven't planned how this will be achieved yet...
// The cookie packing mechanism wasn't built to allow deleting items from the compacted array
// I'm guessing something like set _cookieName[adId] = "false", then unset from packed when recompacting