Why GraphQL document parser throws PartialDataException (PartialDataException(path: __typename))?

Question

I was working on a task related to GraphQL client configuration and this exception: PartialDataException (PartialDataException(path: __typename)) occurred while I was testing the code I wrote, and from then every query I execute throws this exception. I tried to checkout on the stable branch (which didn't contain any code from the task I was working on) but the exception is still thrown.

On my other machine (which is using the stable branch) every query is being executed without any exceptions

So the question is: Why do I receive this exception and how can I fix it?

I am using graphql_flutter to connect to the GraphQL server.