Unable to activate changes on WebLogic

Last week, I was configuring monitoring on server status, and other items we cared about. Some configurations might be wrong so that it was unable to active changes on WebLogic, instead of reporting below errors:

weblogic.management.provider.EditFailedException: Can not undo unactivated changes while an activate changes operation is still in progress

Which made a lock on server configuration, and caused my deployment was failed even restarting it.

Workaround:

cd /pending

rm *.*
and then restart all the servers.

Everything went well again without those changes.