this kind of thing happened to me with delta- northwest merger and i ended up short 80000 miles or so.
I couldnt even begin to try to explain the elaborate mathematics that appeared in my account that resulted in this net loss.
trying to explain was useless.
The moral of the story is; use the miles when you can. they can take them away due to a clerical error and will have no interest, of course, in correcting this.
my experience, anyway.
one thing they have lost, is any future money from me. i only use delta to burn remaining miles. i dont think they're losing much sleep .