Custom quotas keep getting reset

Since we migrated from Owncloud 8 to Nextcloud 9 and upgraded all the way to Nextcloud 12, we are expiriencing a strange problem with custom storage quotas.
The quotas for various users keep getting reset to the default value (1GB). This has happened multiple times since we switched over to Nextcloud about a month ago.
The users that are affected by a reset and the time it takes for it to occur vary. I haven’t been able to see a pattern here aside from the fact that it is always only some users that have their quota reset.

We are using LDAP for authentication but not for the quotas. The corresponding configuration options are empty.

Unfortunately we did not notice the issue when we tested the migration and the upgrades step by step, so we can’t say which step is the root cause of it.

We are currently running the following setup:
Nextcloud version: 12.0
OS: Debian 8
PHP version: 5.6.30
Database: mysql 5.5.55

We are thinking about setting up a new server running Debian 9 but we would like to migrate the database, so the issue most likely would persist.

There was a similar post on ownCloud:

Do you see similar errors in your logs?

I don’t see anything related to storage.php, but a lot of

Argument 8 passed to OCA\Files\Controller\ApiController::__construct() must implement interface OCP\Files\Folder, null given, called in /var/www/owncloud/apps/files/lib/AppInfo/Application.php on line 52 and defined at /var/www/owncloud/apps/files/lib/Controller/ApiController.php#84
Argument 4 passed to OCA\Files\Service\TagService::__construct() must implement interface OCP\Files\Folder, null given, called in /var/www/owncloud/apps/files/lib/AppInfo/Application.php on line 89 and defined at /var/www/owncloud/apps/files/lib/Service/TagService.php#61
Argument 3 passed to OCA\Files\Service\TagService::__construct() must be an instance of OCP\ITags, null given, called in /var/www/owncloud/apps/files/lib/AppInfo/Application.php on line 89 and defined at /var/www/owncloud/apps/files/lib/Service/TagService.php#59
$params["path"] was missing. Transferred value: Array ( [path] => )
Undefined offset: 3 at /var/www/owncloud/apps/activity/lib/FilesHooks.php#620

To be honest I’m quiet surprise to see all these errors. When the problem started I checked the logs and there were no errors, so those that I see now might not be related.

Same with me!

Nextcloud 12
Ubuntu 16.04
PHP 7.0.18
MySQL 5.7.19
LDAP authentication

Please open a bug report on https://github.com/nextcloud/server/issues. If you have a similar error and configuration like in this report (https://github.com/owncloud/core/issues/28380) you can link to it.

It also happens to me: user quota keeps getting reset.

Nextcloud 12
Docker
PHP 7.0
MySQL 5.7.18-0ubuntu0.16.04.1
LDAP authentication

Then please open a bug report.