Well, I've run some tests and I've been able to reproduce the result you've described. Apparently adding TIW alerts in this fashion keeps causing more problems than they're worth. Maybe in a few months we'll find out it's screwed up the SUBROCs too!
Actually, no, those are used much more by the players so if there was something wrong we'd probably have known about it by now.
LWAMI 3.10 will either remove the TIW alerts on LAMs or have a seeker for coastal targets.