It makes zero sense

Now we know your build plan so on the reset, MW will know how to counter your build!  HAH!

As far as I can tell, the bug has been resolved. Thanks for all the input to help me solve this. If you want the full specifics on the bug, let me know

My conclusion is that the bug has always been around, but only occurs under specific conditions.

If a player deletes while having pre-built and another player joins that family, taking over that particular planet in the home system, those buildings still get built on that planet even though the owner has changed. Has to do something with timing. In this case because MW was increased in size twice, a certain intensity on deletes and quick joining created these specific conditions.

In the end the bug itself was just old flawed code.

There could be other conditions resulting in triggering the same flawed code. I checked the buildings that Dukey had and they were all constructed by an unknown player that was already deleted by the system. It is hard too determine much more than that since hardly any info about that deleted player is still available.

When buildings are built they are put in a queue with a timer (construction time) when it reaches 0, they are built. This actual building was based on planet coords and missed some double checks like whether the owner of the construction order was the same as the owner of the planet. Either way someone placed the buildings in the queue for that specific planet.