403 error when embedded

[marylou]

We would like to embed our kimai installation in our normal work environment.
Embedding other sites works just fine.
With kimai, the login page shows but we cannot login.
When we try to log into an embedded kimai installation with Google SAML, we get a 403 error.
When we try to log into an embedded kimai installation without Google SAML, nothing happens when we type in the correct usernames and passwords.
Any suggetions what we can do to make it work?
I wonder if it is related to this issue.
Thanks!

[murgero]

First thing that comes to mind is this: https://docs.cloudron.io/apps/#custom-csp