Greetings,
This is called port sense. Its part of the sound driver installation.
Things to consider.
Some BIOS have a settings that allows you to switch between AC'97 and HD audio
The PIN out configuration on the cases plug doesn't match what the motherboard audio connector is expecting
Something is damaged, bent, shorting or malfunctioning.
To troubleshoot, shutdown and disconnect the front panel audio connector. Power up again and see if the behavior continues. Suggest you test the ports on the I/O panel as well.
Port sense can be disabled on the Sound driver, but I would try to correct the issue instead of masking it.