JSM users automatically added to "normal" users, causing issue invisibility

[Toon Berghman]

Hello

The last months we encounter something that we can not reproduce, we don't have a clue what's causing this, and we don't know how to resolve.

On unknown moments, our customers (that are Jira service management users) appear automatically in the "normal" user list, and this causes that they can't see any issues anymore.
They are able to login, but receive an error code like "we couldn't find any requests" when they want to search for issues via the Request screen.
The filters in the request screen are not specified.

When we check the list of the "normal" users, we see that these users are added.
When we delete them, once again they have access to all the necessary issues.

These users are really random; one specific user of an organization, then 2 users of another organization, then again that 1st user, ...

Any idea what can cause this?
Is there a configuration that needs to be set?

Thanks in advance,
Kind regards?
Toon

[Toon Berghman]

No explanation / solution so far, can anybody help?
If you need more info/pictures/..., please ask!
Thanks in advance,
Kind regards, Toon

[Toon Berghman]

This could be related to the same user trying to register for more than 1 time.
I'm investigating with test-users on our operational system, but in case you have experience / solutions: please share!

Thanks in advance,
Gr,
Toon