> What you describe is a worn bearing with an excess of play, not a seized one

Yeah. Worn or seized bearings are relevant to rotation, but on second thoughts, rotation isn't the issue here.

Rereading the PDF, I can see that I entirely misunderstood the function of the bearing and how it failed, and I suspect I've mislead you. The two lugs mislead me! I would guess they make the lug as two parts for redundancy (if the lug was a single part then it's failure would be bad). My previous comment was wildly incorrect about rotation, but now I think rotation is not the issue.

The casing split in half all the way around the circumference at the weakest point (where the recess is), splitting into two pieces, a forward half and a rearward half. The half forward of the split moves forward and the half rearward of the split moves rearward. That is what they inspect for every sixty months to see if the bearing casing has broken.

An unbroken casing is normally prevented from moving forward or backwards by the ball (how the hell do they make the bearing like that?!).

It appears that the unbroken casing itself is designed for the outside to be able to slide forwards and backwards within the lugs (very little movement?).

The primary force this bearing is preventing is pitching of the engine relative to the wing (vertical force). And secondarily to prevent yawing of the engine relative to the wing (horizontal force). Rotation (roll of the engine relative to the wing) has to be prevented by the main mount and the engine surely can't twist much therefore I suspect rotational forces at that bearing are rather irrelevant.

As the engine thrusts and stops thrusting, the thrust changes create pitching forces on the engine, and there would be vertical movement at the broken bearing - a clunk!?

The main mount would flex a little more due to the extra pitch movement; and I guess we'll have to wait and see whether the bearing failure is relevant to the crash. It appears to be a smoking gun, but could be a red herring?

The main mount is obviously not supposed to fail even if that bearing has broken.