While I was using it, the planer started making a fwap-fwap-flap sound. Upon further inspection, it turns out that on of the three drive belts is frayed.
Since I didn’t know if we had any belts (sorry, I didn’t look) and it didn’t seem like a major issue, I buttoned it back up and did the last two passes on my board. It got quiet for the next user, but he said he didn’t notice anything that sounded like the belt breaking.