Requested API is not supported in Admin On-Behalf-Of mode

We have recently started getting a 401 response with "Requested API is not supported in Admin On-Behalf-Of mode" when calling certain Microsoft endpoints. Specifically,

GET https://graph.microsoft.com/beta/chats/{channelId}/messages/{messageId}
GET https://graph.microsoft.com/v1.0/users/{userId}/joinedTeams
GET https://graph.microsoft.com/v1.0/me/joinedTeams

However this one works

GET https://graph.microsoft.com/v1.0/me

Some information about the setup:

1. We are using a token with delegated scopes

2. The token has the required permissions:

   AppCatalog.ReadWrite.All ChannelMessage.Send Chat.Create Chat.Read Chat.ReadWrite ChatMember.ReadWrite Files.Read.All Files.ReadWrite Sites.Read.All Sites.ReadWrite.All Team.ReadBasic.All User.Read User.Read.All User.ReadBasic.All User.ReadWrite.All profile openid email

3. This has previously worked with the same token

4. This is happening on the v1.0 and beta endpoints

5. We tried removing admin consent from each scopes but still faced the same issue

I cannot find any information in the MS documentation regarding Admin On-Behalf-Of mode and wondered if anyone could shed any light on what we could be doing wrong?

Further Update.

We have now been able to reproduce this on a tenant and has to do with external guest users. These users are able to authenticate into the tenant but you cannot use the token obtained to call some of the Graph API endpoints - Anyone know why this is?

We have tried changing all the settings in External Identities in AAD but still getting the same response on the Graph API endpoints