Unhandled rejection while creating or search for user

Hello, we encounter a problem when Keycloak API does not return the correct response while creating or searching some emails.

I couldn't find any relevant issue to this, so don't know if it's already fixed in the future versions. 

It happened very randomly for some users. 

Edit:

To confirm I have all proper privileges I attached a screen-recording where I cannot create duplicate or add not existing user and everything went ok. 

Edit 2:

i can see that this user already exists in the LDAP directory, but for some reason is not in the keycloak and after deleting his entry from LDAP it was ok.