I'm having the same issure where mine are building a BP of a ship and they would build the parts the wrong way for example i noticve onf of the lights in my ship i was building was not on the ceiling but on the sides

Also having this issue with many blocks.

Dont mess with the projections orientation, dont touch yaw/pitch etc, only the cardinal direction sliders. This is a workaround

As long as you never use Pitch/Yaw/Roll to change your projections when you place them, then everything works as it should.

The moment you touch any of those, all blocks gets inverted.

If your projection is upside down, remove the projector and turn it upside down to fix it.