I found my mistake in reassembling the rear axle assembly. I put a washer on the wrong side of the axle, primarily because the drawing from Morgan leaves it out.

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I put the third washer on the drive belt side and it should have been on the brake side of the axle. It is number 11 part on the exploded view and that view only shows 2 washers where there should be three. I added it in this crude sketch but I believe you get the idea. The third one should be between the adjuster and the drum backing plate mechanism.

The light at the end of the tunnel is actually a train. 2019 M3W