Calendar: Failed to import the event

[rcubeuser]

Hi, installed and configured calendar with these steps:

https://github.com/kolab-roundcube-plugins-mirror/calendar

Then I had this error:
https://www.roundcubeforum.net/index.php?topic=24600.0

And I fixed with @tcd steps.

Now there is a problem with some actions from events invitations (.ics invitations emails), actions like: Accept, Maybe, Decline,  Update the participant status, it throws Failed to import the event

And in my logs I have:

Faild to import the event

[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442
[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/webmail/vendor/sabre/vobject/lib/Parser/MimeDir.php on line 442

[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  Return type of Sabre\VObject\ElementList::offsetSet($offset, $value) should either be compatible with ArrayIterator::offsetSet(mixed $key, mixed $value): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/webmail/vendor/sabre/vobject/lib/ElementList.php on line 28

[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Deprecated:  Return type of Sabre\VObject\ElementList::offsetUnset($offset) should either be compatible with ArrayIterator::offsetUnset(mixed $key): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/webmail/vendor/sabre/vobject/lib/ElementList.php on line 40

[13-Mar-2024 11:31:00 Europe/Helsinki] PHP Warning:  Trying to access array offset on value of type null in /var/www/webmail/plugins/calendar/calendar.php on line 3648

P.S.  I'm using php 8.1 fastCGI