[Bug] Multiplayer breaks as soon as first building is placed

When playing with two people everything seems to work alright with harvesting and placing stockpiles and assigning jobs, but as soon as a building is placed the error below appears and no building can be built because of it.

This is the bug that pops up.
release-837 (x64)
radiant/modules/validator.lua:67: argument #1 expected type string but received userdata
stack traceback:
[C]: ?
[C]: in function ‘error’
radiant/modules/validator.lua:67: in function ‘assert_type’
radiant/modules/validator.lua:8: in function ‘expect_argument_types’
stonehearth/call_handlers/build_call_handler.lua:8: in function <stonehearth/call_handlers/build_call_handler.lua:7>