It seems the object LOD was changed a few updates ago, so very small airport objects (including taxiway signs) only appear very close to the camera. It cannot be improved by increasing object LOD slider.
I remembered at the time Asobo said that Xbox / PC would allow different behaviours for LOD, but I don’t know what happened in the end. The LOD could definitely be improved on PC because many airport objects pop into view far too close to the camera. It’s also visible on fences and larger airport buildings.