Interface Scenario with Capella 5.2

Hello, I’m a new Capella User. I used Interface scenario in the Physical layer. I can insert Sequence messages between an Actor and a Physical component (Yellow box). I was also able to add sequence messages from a Physical component to ITSELF but after sometimes I was not able anymore to insert NEW messages from the Physical component to ITSELF. The Dialog window “Create a Message without return” opens, I click on “create a new message”, I wrote the name of the message but When I click on “OK”, the dialog window doesn’t close. Nevertheless, with a NEW Physical component It worked. Did anybody encounter such issue?
Thanks for your help
Franck