[Teeps]

No clue about your tivo's specific problem.
But if you got 6 years out of the original HDD, then count yourself lucky.
The HDD failed in my XL4 after only 2 years. But with different symptom.

 

[Teeps]

Is HDMI failure common on the Premiere?

I don't recall seeing many complaints logged here.
But, the HDMI output on my XL4 failed after an electrical transformer blew up a few blocks away.
However the incident also took out the HDMI on a computer monitor and TV; also completely nuked a TiVo Roamio that was connected to OTA.