anaconda outputs error window in exiting from spoke, partitioning or network configuration

Issue

• anaconda outputs error as below in exiting from a spoke, partitioning or network configuration, and sometimes it's gone into black screen.

An unknown error has occurred

This program has encountered an unknown error. You may report the bug below or quit the program.

More info...
The output below may help determine the cause of the error:

anaconda 19.31.123-1 exception report
Traceback (most recent call first):
  File "/usr/lib64/python2.7/subprocess.py", line 1205, in _execute_child
    Self.pid = os.fork()
  File "/usr/lib64/python2.7/subprocess.py", line 711, in __init__
    errread, errwrite)
....