Lock message in webclient UI

Hello,

in our productive CRM system we use servicerequest. For some reason since some days we face the following issue:

If one user already has a service request in EDIT mode the second user does not get the message "... is currently locked by... " if he opens the same service request in edit mode. It just stays in display mode without a message.

Could one of you please give me a tip what i need to check?

Thank you.

Kind regards

Manfred