Hmmmmm - you are right twice: The oneway arrow symbols still appear . And as far as I can see, all disappearing roads are tagged with layer=-1.
But - as mentioned before and in the other thread - the disappearing could be fixed by using other maps, but style had no influence. For the Z-Level topic it was vice versa: The used map had no influence, but it could be fixed by using an other style (my first idea was to write both topics in one thread, but now it seems that two threads are better).
But nevertheless I think it is a bug in map generation: Why is the colored line for the street gone only, if I zoom in to zoom level 18 or higher ? And why does it work correctly with map from OpenAndroMaps?
I will try OpenAndroMaps for the next time - but downloading them is not as comfortable as downloading the maps from Kurviger download server. Up to now I thought using the maps from Kurviger server would be the best, because it is the “native” map provider, probably most people use it, so maximum test depth …