Check if your external calendar has duplicated UIDs.

Hi, this external calendar is Confluence TeamCalendars. Do you know easy way to check this?

Manually searching can take a lot. And at time of import this calendar working at SOGo

Ho, I now realize that error has duid. Will check.

You can start by looking at the UID reported in the log.

I find exact calendar that was cause of issue, this even is repeat per year, but there no duplicates in UID. And in all other calendars there no such UID as well

I send to you email with link to anonymized calendar, you can remove your email from thread if you can/want. Paste here some part that send to PM to not lose point:
looks like now I can't reproduce issue, maybe some update fixed it. Calendar reload on login not broke login fully now - SOGo is waiting really long on login screen, but had success to open mail client page. Previously when I initially create this bug SOGo instantly login to mail client page, but all page was white and no matter how many I wait it was still without any content. In any way SOGo will throw more then 1000 errors in log about one such load and consume many resources.

I've subscribe to your calendar. With the latest code, I've seen no error during the import. It took about 30 seconds on my machine to import the calendar.

After my last test I too not get blocked on login screen, but get 1000 errors in SOGo log about duplicates, did you get them as well? Or this only reproduce in my case? Thank you.