During system testing of automotive electrical control units various reasons can lead to invalid test failures, e.g., non-responding components, faulty simulation models, faulty test case implementations, or hardware or software misconfigurations. To determine whether a test failure is invalid and what the underlying cause was, the test executions have to be analyzed manually, which is tedious and therefore costly. In this work, we report the magnitude of the problem of invalid test failures with four system testing projects from the automotive domain. We find that up to 91% of failed test executions are considered invalid. An oftentimes overlooked challenge are unreliable test infrastructures which deteriorate the validity of the test runs. In the studied projects already between 27% and 53% of failed test executions are linked to unreliable test infrastructures.