We have a lot of regressiontests about seafaring (for a reason :-)
./regression_test.py -b ./widelands 

FAILs

test/maps/ship_transportation.wmf/scripting/test_rip_ports_with_worker_in_transit.lua ... 
test/maps/ship_transportation.wmf/scripting/test_rip_first_port_with_worker_in_portdock.lua ... 
test/maps/ship_transportation.wmf/scripting/test_rip_first_port_with_ware_in_portdock.lua ... 
test/maps/ship_transportation.wmf/scripting/test_rip_second_port_with_ware_in_portdock.lua ... 
test/maps/ship_transportation.wmf/scripting/test_rip_farm_with_ware_and_worker_in_transit.lua ... 
test/maps/ship_transportation.wmf/scripting/test_rip_ports_with_ware_in_transit.lua ... 

test/maps/ship_transportation.wmf/scripting/test_rip_second_port_with_worker_in_portdock.lua ... 

One hard crash from ASAN with:
==14492==ERROR: AddressSanitizer: heap-use-after-free on address 0x6040020e6798 at pc 0x000107e3088e bp 0x7ffeea4f2790 sp 0x7ffeea4f2788
READ of size 8 at 0x6040020e6798 thread T0
    #0 0x107e3088d in std::__1::__tree_end_node<std::__1::__tree_node_base<void*>*>* std::__1::__tree_next_iter<std::__1::__tree_end_node<std::__1::__tree_node_base<void*>*>*, std::__1::__tree_node_base<void*>*>(std::__1::__tree_node_base<void*>*) __tree:176
    #1 0x107e1c53a in std::__1::__tree_const_iterator<Widelands::Ship*, std::__1::__tree_node<Widelands::Ship*, void*>*, long>::operator++() __tree:920
    #2 0x107e1bc2c in Widelands::PortDock::cleanup(Widelands::EditorGameBase&) portdock.cc:200
    #3 0x1074fcef2 in Widelands::MapObject::remove(Widelands::EditorGameBase&) map_object.cc:465
    #4 0x1078b2d7c in Widelands::Warehouse::cleanup(Widelands::EditorGameBase&) warehouse.cc:638
...
previously allocated by thread T0 here:
...
    #4 0x107e3340f in std::__1::unique_ptr<std::__1::__tree_node<Widelands::Ship*, void*>, std::__1::__tree_node_destructor<std::__1::allocator<std::__1::__tree_node<Widelands::Ship*, void*> > > > std::__1::__tree<Widelands::Ship*, std::__1::less<Widelands::Ship*>, std::__1::allocator<Widelands::Ship*> >::__construct_node<Widelands::Ship*>(Widelands::Ship*&&) __tree:2201
    #5 0x107e32bfc in std::__1::pair<std::__1::__tree_iterator<Widelands::Ship*, std::__1::__tree_node<Widelands::Ship*, void*>*, long>, bool> std::__1::__tree<Widelands::Ship*, std::__1::less<Widelands::Ship*>, std::__1::allocator<Widelands::Ship*> >::__emplace_unique_key_args<Widelands::Ship*, Widelands::Ship*>(Widelands::Ship* const&, Widelands::Ship*&&) __tree:2147
    #6 0x107e327ab in std::__1::__tree<Widelands::Ship*, std::__1::less<Widelands::Ship*>, std::__1::allocator<Widelands::Ship*> >::__insert_unique(Widelands::Ship*&&) __tree:1276
    #7 0x107e1eb3f in std::__1::set<Widelands::Ship*, std::__1::less<Widelands::Ship*>, std::__1::allocator<Widelands::Ship*> >::insert(Widelands::Ship*&&) set:635
    #8 0x107e1e3af in Widelands::PortDock::ship_coming(Widelands::Ship&, bool) portdock.cc:330
    #9 0x10772d84b in Widelands::Ship::push_destination(Widelands::Game&, Widelands::PortDock&) ship.cc:763
    #10 0x107df0509 in Widelands::Fleet::push_next_destinations(Widelands::Game&, Widelands::Ship&, Widelands::PortDock const&) fleet.cc:872
    #11 0x107e1fa50 in Widelands::PortDock::ship_arrived(Widelands::Game&, Widelands::Ship&) portdock.cc:374
    #12 0x10772239d in Widelands::Ship::ship_update_transport(Widelands::Game&, Widelands::Bob::State&) ship.cc:315
    #13 0x107720fb8 in Widelands::Ship::ship_update(Widelands::Game&, Widelands::Bob::State&) ship.cc:265
    #14 0x107458bff in Widelands::Bob::do_act(Widelands::Game&) bob.cc:194
 
Caused by FAIL: test/maps/ship_transportation.wmf/scripting/test_rip_portdock_with_worker_and_ware_in_transit.lua

Please tell me how I may help you....