Abra o borders.xml na pasta da sua versão (RME/data/versão)
Procure por
<border id="5"> -- Sea border --
<borderitem edge="n" item="4644"/>
<borderitem edge="e" item="4645"/>
<borderitem edge="s" item="4646"/>
<borderitem edge="w" item="4647"/>
<borderitem edge="cnw" item="4652"/>
<borderitem edge="cne" item="4653"/>
<borderitem edge="csw" item="4654"/>
<borderitem edge="cse" item="4655"/>
<borderitem edge="dnw" item="4648"/>
<borderitem edge="dne" item="4649"/>
<borderitem edge="dsw" item="4650"/>
<borderitem edge="dse" item="4651"/>
</border>
Substitua tudo por esse:
<border id="5"> -- Sea border --
<borderitem edge="n" item="4632"/>
<borderitem edge="e" item="4635"/>
<borderitem edge="s" item="4634"/>
<borderitem edge="w" item="4633"/>
<borderitem edge="cnw" item="4643"/>
<borderitem edge="cne" item="4642"/>
<borderitem edge="csw" item="4641"/>
<borderitem edge="cse" item="4640"/>
<borderitem edge="dnw" item="4639"/>
<borderitem edge="dne" item="4638"/>
<borderitem edge="dsw" item="4637"/>
<borderitem edge="dse" item="4636"/>
</border>