Observed on a clean copy of 2.0 Alpha 1 - NM900 missiles launched from Britannias at a Phobos were disappearing. On closer inspection, the disappearing missiles were proximity detonating but were not spawning their explosions at the point where they detonated.

Further observation confirmed this behaviour with non-tracking and non-radius fragmenting missiles, and that it doesn't happen with non-fragmenting missiles. It is most visable against long and thing ships like the Phobos or Polar when missiles are launched from the side of the target, but this may or may not be an indication of what triggers it.

(Aury got ahead of me with https://ministry.kronosaur.com/record.hexm?id=104160 but didn't actually describe the bug at all so I'm doing this properly)

Screenshots:

These two screenshots were taken from a recorded clip of the 2.0 Alpha 1 intro screen, and are one frame apart. In the first frame we see an NM900 missile inbound. In the second screenshot the missile has disappeared and an NM900 radius fragment explosion has appeared centred on the dead britannia next to the target Phobos, well away from where the missile was.