Light Build not fully there on reload

Hi
When I build lighting only, save, close and reload the project I get a ‘Lighting needs to be rebuilt, 256 objects need lighting’ message.

I’ve read that this could be because there are moving objects in the project that have been mistakenly marked as ‘static’, but so far I have been unable to find anything that fits that description.

The project comprises of one exterior area, followed by a large number of interior rooms, there’s a bit of foliage, a lot of lights, only one or 2 of which are moveable, a lot of the rooms are premade blueprints, nothing too crazy.
Any suggestions on how to fix this would be greatly appreciated.

Regards,