It seems like $transaction of type Pronamic\WordPress\Pay\G...ultiSafepay\Transaction is incompatible with the declared type Pronamic\WordPress\Pay\G...nsactionResponseMessage of property $transaction.
Our type inference engine has found an assignment to a property that is incompatible
with the declared type of that property.
Either this assignment is in error or the assigned type should be added
to the documentation/type hint for that property..