This sounds like a bug in the upstream Terraform resource provider - would be worth making sure there is an issue tracking it.
I don’t have any great workarounds to suggest - other than making sure the two updates are deployed separately which is definitely not ideal.
There are more complicated things you could try - like using a get method to look up the existing resource and then conditionally setting the new value for the conflicting property on whether the existing and new value of the other property match. That may well be more complicated than it’s worth though.
What is the resource in question?