Malcolm
I have a new 1974 Maytag A107.....and sometimes it depends on the load the tub will index, other times locked tight in place, seems the brake doesn't always lock tight from the spin, I used to think it was with older machines where they are wearing out, but having a "new" one do it, somewhat seems normal for every now and then to see it index....normally you would never see this cause the machine only operates with the lid closed, actually I noticed it with the front cover off and I seen the tranny moving during agitation, I wouldn't worry about it unless its doing it on every load, even with an empty tub....then you may consider replacing the brakes....