event reminder is missing in a shared calendar w/o edit rights

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Steps to reproduce

1. User1 creates a new calendar
2. User1 creates a new event with a reminders
3. User1 shares the calendar to User2 as non-editable

Expected behaviour

User2 shall also get the reminder. Hint: This was already working - a while ago.

Actual behaviour

User2 don't see/get any reminder. Only User1 get the reminder.
User2 will get the reminder if User1 set the calendar to editable.

Server configuration

Docker container: nextcloud:19.0-apache, nextcloud:21-apache

Operating system:

Web server:

Database: mariadb:10-bionic (docker container)

PHP version:

Nextcloud version: 19.0.1, 21.0.2

Updated from an older Nextcloud/ownCloud or fresh install: continuosly updating from older version.

Where did you install Nextcloud from:

Signing status:

Login as admin user into your Nextcloud and access 
http://example.com/index.php/settings/integrity/failed 
paste the results here.

List of activated apps:

If you have access to your command line run e.g.:
sudo -u www-data php occ app:list
from within your Nextcloud installation folder

Nextcloud configuration:

If you have access to your command line run e.g.:
sudo -u www-data php occ config:list system
from within your Nextcloud installation folder

or 

Insert your config.php content here. 
Make sure to remove all sensitive content such as passwords. (e.g. database password, passwordsalt, secret, smtp password, …)

Are you using external storage, if yes which one: local/smb/sftp/...

Are you using encryption: yes/no

Are you using an external user-backend, if yes which one: LDAP/ActiveDirectory/Webdav/...

LDAP configuration (delete this part if not used)

With access to your command line run e.g.:
sudo -u www-data php occ ldap:show-config
from within your Nextcloud installation folder

Without access to your command line download the data/owncloud.db to your local
computer or access your SQL server remotely and run the select query:
SELECT * FROM `oc_appconfig` WHERE `appid` = 'user_ldap';


Eventually replace sensitive data as the name/IP-address of your LDAP server or groups.

Client configuration

Browser:

Operating system:

Logs

Web server error log

Insert your webserver log here

Nextcloud log (data/nextcloud.log)

Insert your Nextcloud log here

Browser log

Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log
c) ...

Reproduce the three-step shared-calendar scenario on Nextcloud 19 or 21, checking data/nextcloud.log and the supplied server configuration details first. Trace the calendar reminder handling for a non-editable share; done means User2 receives the event reminder without granting edit rights.