'gmt coast -S' incomplete water area filling

[mkononets]

Hi,
Partial filling of water is observed when filling water areas only is requested:

gmt coast -JG-140/30/18c -Rg -Ssteelblue -A0/1/1 -B30g30 -png water

water.png with partial water filling:

same with -JQ...:

gmt coast -JQ18c -Rg -Ssteelblue -A0/1/1 -B30g30 -png water_JQ

Filling looks correct when both water and land filling is requested:

gmt coast -JG-140/30/18c -Rg -Ssteelblue -Glightred -A0/1/1 -B30g30 -png water+land

water+land.png:

Land only also filled correctly:

gmt coast -JG-140/30/18c -Rg -Glightred -A0/1/1 -B30g30 -png land

land.png:

[mkononets]

Same problem with water+land when water transparency is requested. Presence of coastline does not seem to affect it:

gmt coast -JG-140/30/18c -Rg -Ssteelblue@70 -Glightred -Wfaint -A0/1/1 -B30g30 -png water+transparency+land+coastline

water+transparency+land+coastline.png:

[mkononets]

Land transparency also triggers the bug:

gmt coast -JG-140/30/18c -Rg -Ssteelblue -Gred@70 -A0/1/1 -B30g30 -png water+land+transparency

water+land+transparency.png:

[mkononets]

There's something that looks as a grid in the background, exactly 10 degrees grid spacing. Many grid cells with no land have no water filling, but not all!:

gmt coast -JG-140/30/18c -Rg -Ssteelblue@70 -Gred@70 -A0/1/1 -png water+transparency+land+transparency

water+transparency+land+transparency.png:

gmt coast -JG-140/30/18c -Rg -Ssteelblue@70 -Gred@70 -A0/1/1 -B10g10 -png water+transparency+land+transparency+10_deg_grid