move an appointment from one user to another

I have two users "A" & "B".
Each of them has a shared calendar with each other.
if I write an appointment for "A" and after a few hours or a few days I want to move it to the calendar of "B" and vice versa directly on NextCloud -> App Calendar , the appointment disappears only from the OneCalendar app, it remains on NextCloud -> Browser-based Calendar app.
I have been using calendar since version 2.0.5 and it has always given me this problem.
I currently use NextCloud Version 25.0.3 and Calendar 4.2.2 and OneCalendar 4.3.4 Premium.
what can I do ?