Hi @ecerulm,
This seems like something that was more likely to be caused by a provider upgrade rather than a Terraform upgrade. Did you happen to also upgrade the AWS provider at the same time?
It is possible that this sort of change could result from a bug fix to Terraform Core, if something was not being compared correctly before, but AFAIK Terraform has been treating"" as different to null since Terraform 0.12 (which is the release that introduced null), and so that’s why I’m suspecting that it may be a change of behavior in the provider or in the provider SDK.
If we can narrow down exactly what caused this change in behavior then I may have a better suggestion, but for now I think the only general idea I have is to change the configuration to match the prior state, by writing out the empty string values of these arguments explicitly:
gateway_id = ""
# etc
Not ideal by any means, so I’m hoping we can find a better solution by narrowing down the cause.