[Koha] Hold problems

[Ketut Gunawan]

Dear all,

 I need a help.  I have problems with Koha's Hold feature. Patron can place a hold but cannot cancel it.
For cancelling a hold the message is: "Sorry, the requested page is not available. Error 500"

Staff can check in a hold, bu cannot:
- check out a hold
- suspend a hold
- delete a hold
For these the error message is: "An error has occurred! Error 500 

How to solve this problem? Any clue and help would be greatly appreciated.
I install the latest Koha (21.05) in docker. Thank you.

Best regards,
K. Gunawan