Did you maybe find a solution for this problem? I have the same problem on my mobile: sea marks are only visible at certain zoom levels. For example I see some green ton at level 15 but not a yellow one, while at level 16 I can see the yellow one but not the green one.
I'm hoping that you found some solution because it would make Oruxmaps very useful while sailing
I've got questions/bugs concerning the appearance of sea marks like tons in different zoom settings.
I've tested with the latest oruxmaps blue and a map of the river mosel in the city koblenz/germany but other german seaways show the same behavior.
1. Online Map "MxM Openseamap & Base Map":
On zoom level 16 I see no sea marks at all.
On zoom level 17 I see some sea marks(red and green tons) but not that yellow ton I see on level 15.
On zoom level 15 I see only a few sea marks like a yellow ton but not the red and green ones from level 17.
2. Downloaded Offline Map:
I downloaded a part of the above online map with the oruxmaps map creator. Zoom levels 10-16.
I can only see some (not all) sea marks on zoom level 16.
Any other zoom level does not show any sea marks.
The drawing of the sea marks is so weird that nautical use is nearly impossible. Can you please fix this?