RDS Blue/Green deployment on a very large Database seems too long

Hello, We are trying to use the new RDS Blue/Green Deployments feature to upgrade Aurora Mysql 5.6 to 5.7. We did some tests on a small DB (a few GiB) and everything worked fine. So we tried running a Blue/Green on a 3.6 TiB Database (with billions of rows), but it seems RDS can't create the Green instance, it's been on status Provisioning for 6 days now and we can't find any progress information, we guess things are "blocked".

Should we wait longer ? Is there any limitation on the DB size to use Blue/Green deployment ?