Can you tell us which version you are migrating from and if you also upgraded your console version? If this was working before the migration, I'd suggest to check that the console and server versions are the same.
Do you have this issue on other deliveries too? If this is the case, I'd suggest to contact Support.
If this is on one specific delivery, can you try creating a new delivery and to paste the html content of the one you have problems with in a new one?