osmarender - problem with coastline

I don’t know what to do to fix the coastline of my island.
Some days, it displays well, others, no.
This is the URL :
The coastline is not opened somewhere. The sea is on the right of the line. No point related to the land is on the sea. I’ve just tried to reduce the length of the roads which are close to the coastline, but yesterday, it didn’t work, so today I suppose it will not work. A bug to the osmarender stuff ? Francois