User invalid after replacing openid (gitlab) server

After replacing our openid (GITLab) Server to another server all our user are not valid anymore.
The users were not able to login. Mattermost complained that another already exists with the same email.

mattermost-test-app | {“level”:“error”,“ts”:1589537313.6748028,“caller”:“web/oauth.go:271”,“msg”:“CreateOAuthUser: There is already an account associated with that email address using a sign in method other than gitlab. Please sign in using gitlab.,”}

I had to delete the user and it worked. Is there a way to safe the data of the user?