What steps will reproduce the problem?
(1) Open Dome, select a board (ok if empty)
(2) Click UPDATE on a component, for example HWID
(3) Upload a garbage file for it.
(4) Dismiss the error, remove the task on right-bottom corner.
(5) Click UPDATE again
(6) Upload a correct file

What is the expected result?
Success

What happens instead?
Failure:

Internal Server Error

{"detail":"Cannot stage config file, make sure no one is editing Umpire config at the same time, and there is no staging config exists. Error message: <Fault -32500: 'Traceback (most recent call last):\\n  File \"/usr/lib/python2.7/site-packages/twisted/web/resource.py\", line 250, in render\\n    return m(request)\\n  File \"/usr/lib/python2.7/site-packages/twisted/web/xmlrpc.py\", line 167, in render_POST\\n    d = defer.maybeDeferred(function, request, *args)\\n  File \"/usr/lib/python2.7/site-packages/twisted/internet/defer.py\", line 150, in maybeDeferred\\n    result = f(*args, **kw)\\n  File \"/usr/local/factory/py_pkg/cros/factory/umpire/web/xmlrpc.py\", line 90, in _WrapProcedure\\n    result = defer.maybeDeferred(method, *args, **kwargs)\\n--- <exception caught here> ---\\n  File \"/usr/lib/python2.7/site-packages/twisted/internet/defer.py\", line 150, in maybeDeferred\\n    result = f(*args, **kw)\\n  File \"/usr/local/factory/py_pkg/cros/factory/umpire/rpc_cli.py\", line 166, in StageConfigFile\\n    self.env.StageConfigFile(config_path, force=force)\\n  File \"/usr/local/factory/py_pkg/cros/factory/umpire/umpire_env.py\", line 245, in StageConfigFile\\n    self.staging_config_file)\\ncros.factory.umpire.common.UmpireError: Unable to stage a config file as another config is already staged. Check \\'/var/db/factory/umpire/staging_umpire.yaml\\' to decide if it should be deployed (use \"umpire deploy\"), edited again (\"umpire edit\") or discarded (\"umpire unstage\").\\n'>"}
... even if the task is canceled
umpire status
Staging config exists (umpire.711dcfe3e8eef1f40dfe152f5cd0c918.yaml)

Youcheng thinks this is a bug in Dome.