Space Engineers – Why Space Station Converts to Ship and Drifts Away

I am playing the "Star System" scenario offline in Survival mode with meteor showers enabled.

I started out on the earth-like planet, but I have just left it and built a space station in orbit above it on an altitude of about 55 km (measured from the GPS waypoint I put at my old station on the ground). It is already of a quite decent size with a pressurized command center, artificial gravity, docking ring, assemblers, refineries and gatling gun turrets.

However, it has happened twice to me now that the space station suddenly started to drift and rotate. I noticed in the "Info" tab of its terminal that it was suddenly converted to a ship. Both times I managed to stabilized it using a docked ship and turn it back into a station by clicking "convert to station" in the terminal.

What could be the reason for the station turning into a ship and what can I do to prevent it from happening again?

Some things which I suspect to have something to do with it but could also be coincidences:

• The first time I was just making some architectural changes to the station where I was deconstructing and replacing a lot of blocks.
• The second time it appeared as if the station just suffered some minor damage from a meteor shower. I wasn't present at that time but nearby (mining an asteroid about 5km away).