When cancelling Qt5 from Coin UI scheduler goes stuck for a long time

thriftpy.transport.transport.TTransportException: TTransportException(type=1, message='Could not connect to 10.215.163.15:49801')
 2018-10-05 09:55:17,947 ERROR:application(5973): Connection to an agent failed
 Traceback (most recent call last):
 File "src/scheduler.py", line 191, in agentHeartbeat
 workItem = self.workItems[buildKey]
 KeyError: 'qt/qtbase/11af7275a8f80c6004277d6d1bb22df6d2c16f6f/MacOSMacOS_10_12x86_64MacOSMacOS_10_12x86_64Clangqtci-macos-10.12-x86_64-8-e96fa2DeveloperBuild_NoFramework_Release_QtNamespace_NoPch/2a48a3b7dcb9652b1532a3ad14de7580b5b9b1ee/Test'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
 File "/home/vmbuilder/qt-ci/env/lib/python3.6/site-packages/thriftpy/transport/socket.py", line 74, in open
 raise e
 File "/home/vmbuilder/qt-ci/env/lib/python3.6/site-packages/thriftpy/transport/socket.py", line 69, in open
 self.handle.connect(res[4])