Activities with input field values that contain a new line can't be updated in Process Automation Designer. For any Process in Process Automation Designer, if an activity has an input variable value that contains new lines (/n or /r) it would fail to be re-arranged. In this situation, you would get a general network error and the activity is not re-ordered. This problem only happens on Paris release.
The following general network error would be displayed when the issue is happening:
"Error: A network error occurred. Please refresh the page or contact your System Administrator if this problem continues."
You will see the general network error and the activity is not reordered.
You would have to check each individual activity within the process, identify those with input variable value containing new line and remove new line accordingly.