4025 CONSTRAINT oc_share.attributes: Unable to add federated share to my Nextcloud

Hi there,

a not so tech-savvy friend of mine has a hosted Nextcloud at the same provider as me (Hetzner). Now when he tries to share a folder to me, I can use the share via the web frontend, but when I try to add the share to my own Instance, I get the following error message:

Failed to add the public link to your Nextcloud
An exception occurred while executing a query: SQLSTATE[23000]: Integrity constraint violation: 4025 CONSTRAINT `oc_share.attributes` failed for `nx55161`.`oc_share`

(nx55161 being the name of his hosted instance)

This happens for all of his shares when I try to add them.

Through the provider I can access the OCC console, are there any commands I can try before asking the provider for support?

Thank you
Thea