It can be difficult to determine the cause of an issue that is not consistent. The best thing you could do to help determine what the problem is would be to try and reproduce it with some type of regularity. Could you make a backup of your db then test with the records that you have. When you are testing you should do a multiple delete then check the db to ensure that they have all been deleted. Make sure to keep track of how you are deleting the records in case there is a problem with an individual record. As soon as you can get the problem to occur with some consistency we will be able to help you look into the cause of the issue. Please post back and let us know the results that you get during this testing.