Thanks for running some tests on this, it's always nice to have people try to run some things down a bit and give us enough information to try to reproduce the effect.
LAMs that detonate at a waypoint instead of striking a particular object do AOE damage (they have to, in order to hit anything), so it's not unusual to damage adjacent buildings. The higher damage level will increase the AOE damage.
Funny story, while doing 3.09 I was re-doing the damage levels for mines, and one of them (I forget which, maybe the Mobile Mine) had a massive, massive warhead that needed to be turned up quite a bit for the damage to be accurate relative to other underwater weapons. Influence mines, like LAMs, don't hit their targets directly but detonate and do AOE damage, so I tested the weapon in a harbor with several ships nearby. When the damage-adjusted mine exploded, it sank every ship in the harbor (which was probably a few miles across). To see how bad it really was, I put several buildings along the coast and tried it again... most of the buildings were severely damaged. I decided the mine as adjusted was basically a tactical nuke and kept the damage artificially low to minimize the AOE (ships in the same formation can still be damaged, but the effect won't go for miles). So, if you ever see a ship get hit by a Mobile Mine in 3.09+, just remember, however much damage it got, it got off light.
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