Calendar makes Problems at creating new meetings

Hi,
today I got a problem on a calendar of one user.
while he tries to create new meetings there the webapp creates many entries in the calendar.
The Webapp shows connecting problems and reconnections.

I tried : System reboot, cleaning of the browser cache, browser changing, changing of client pc…
always the same problem but only for that user account.

Then I tried the kopano-fsck -u username --calendar --checkonly
Result: 75 problems
then without checkonly: 75 problems fixed as result.

But the error still occurs.
With the z-push , the calendar of that user can be used normal and new meetings can be created withput any problem.

E-Mail and other calendars work fine with that account.
It seems to be a cache problem of that calendar in webapp???

WebApp: 3.3.0.616-437.1
Kopano Core: 8.4.0-344

Some ideas would be great!

Regards Karsten

Hi, today there is no problem. everything works fine.

Question: Is there a internal webapp cache that can travel with the user to other machines? (Like used e-mail adresses) ? And is it possible to refresh it?

Any Idea what happened?

Regards