Failed to save schedules in Resource Membership Update

Greetings,

I did a Run on all 3 schedules in Resource Membership Update. After that, I clicked on the OK button. However, it displayed 3 error messages as below:

•Failed to save the delta scheduled item. Please check the log for more details.
•Failed to save the complete scheduled item. Please check the log for more details.
•Failed to save the policy scheduled item. Please check the log for more details.
 

The messages from log file as attached:

What is the cause of this error? It did not happened before previously.