We have 2 galaxy instances running

one is
v15.05-74-gf6b894a
the other is
v15.10-30-g6a47d2d

a user is trying to import a workflow file, it works on the older one, but raises an error on the newer one.

URL: http://redacted.edu:8080/workflow/import_workflow

File '/cluster/home/galaxy/galaxy/lib/galaxy/web/framework/middleware/error.py', line 151 in __call__
  app_iter = self.application(environ, sr_checker)
File '/cluster/home/galaxy/galaxy/eggs/Paste-1.7.5.1-py2.7.egg/paste/recursive.py', line 84 in __call__
  return self.application(environ, start_response)
File '/cluster/home/galaxy/galaxy/eggs/Paste-1.7.5.1-py2.7.egg/paste/httpexceptions.py', line 633 in __call__
  return self.application(environ, start_response)
File '/cluster/home/galaxy/galaxy/lib/galaxy/web/framework/base.py', line 133 in __call__
  return self.handle_request( environ, start_response )
File '/cluster/home/galaxy/galaxy/lib/galaxy/web/framework/base.py', line 191 in handle_request
  body = method( trans, **kwargs )
File '/cluster/home/galaxy/galaxy/lib/galaxy/webapps/galaxy/controllers/workflow.py', line 921 in import_workflow
  workflow, missing_tool_tups = self._workflow_from_dict( trans, data, source=src, add_to_menu=add_to_menu )
File '/cluster/home/galaxy/galaxy/lib/galaxy/web/base/controller.py', line 1111 in _workflow_from_dict
  publish=publish
File '/cluster/home/galaxy/galaxy/lib/galaxy/managers/workflows.py', line 159 in build_workflow_from_dict
  module, step = self.__module_from_dict( trans, step_dict, secure=False )
File '/cluster/home/galaxy/galaxy/lib/galaxy/managers/workflows.py', line 605 in __module_from_dict
  module.save_to_step( step )
File '/cluster/home/galaxy/galaxy/lib/galaxy/workflow/modules.py', line 592 in save_to_step
  step.tool_inputs = self.tool.params_to_strings( self.state.inputs, self.trans.app )
File '/cluster/home/galaxy/galaxy/lib/galaxy/tools/__init__.py', line 1980 in params_to_strings
  return params_to_strings( self.inputs, params, app )
File '/cluster/home/galaxy/galaxy/lib/galaxy/tools/parameters/__init__.py', line 92 in params_to_strings
  value = params[ key ].value_to_basic( value, app )
File '/cluster/home/galaxy/galaxy/lib/galaxy/tools/parameters/grouping.py', line 574 in value_to_basic
  rval[ self.test_param.name ] = self.test_param.value_to_basic( value[self.test_param.name ], app )
KeyError: 'uncol'

i'm not able conclude much from this dump. Can anyone suggest some steps to debug this.

Cheers
Tony Schreiner