Checked today, mine does that as well and everything is adjusted correctly.

You can hear it in this video as well at 54 seconds in.

Not so much. The rollover switch is normally open, and so acts as the 'lock in' switch for whatever the related relay is. When stuck closed, the relay is stuck on, and the armature plate is pulled in. But with the switch blade and spring tension working against it, and being AC, there will be a buzz. The buzz will be louder the more worn out things get (coil windings, indentation in armature plate). And the coil is getting hot during this time too.

That's why when there's a stuck switch there's a corresponding loud buzz as a clue that there's a stuck coil (and thus a stuck switch). They just buzz.

I noted this in your other thread, but just to collect all the data in one place, my Abra Ca Dabra rollovers buzz audibly too.

One thing to note is whether the other ones are daisy-chained relays or not, and whether they're in a relay bank or not. These particular relays are 'series' relays, so have another relay 'behind' them in series (e.g., when 1B trips, the series relay also fires). These series relays are also on a relay bank, so there's also more sympathetic vibration opportunity from the bar and bracket.

Other rollover relays sometimes are just standalone, such that they're the only thing that can be active if the rollover switch is held.

My ACD buzzes. My SweatHearts buzzes. My Kings and Queens buzzes. thats Gottlieb for you.