403 Forbidden Error unrelated to PATs/Permissions

## Description

We are facing the below error when using the GitHub GEI to migrate repositories between GHEC to GHEMU.
 
`Git source migration failed. Error message: the server responded with status 403 Error class: Faraday::ForbiddenError.`

We have validated the PAT for both the source org in GHEC and the target org in GHEMU. This included checking the scope and that it's been SSO authorised - even tested these PATs by performing GH CLI commands against the respective orgs.
 
We are quite certain the issue is in relation to GEI service connecting to the source GHEC/org as the blank repository is being created in the target GHEMU. We have checked IP Allowlist is not enabled within GHEC.

Can further details be provided on the below error?

## Reproduction Steps
Run the command `gh gei migrate-repo --github-source-org SOURCE_ORG --source-repo SOURCE_REPO --github-target-org TARGET_ORG --verbose`