I have a couple of old 78s (recorded about 1917) that have hairline cracks and are warped. When I play them on a professional DJ turntable, the bounce is audible, but the results are much better when played on a consumer-grade player. The reason is that the DJ pickup weight is controlled with a counterweight, while the consumer unit uses a spring. The counterweight adds considerably to the vertical moment of inertia, accentuating the bounce. I would really like to have a spring option for my DJ turntable, to use in those limited cases of warped, but irreplaceable records.
With worn records, it occurred to me that when a shellac record is played, minute chipping occurs on one side of each wiggle in the groove, but not on the other. Examination under magnification seemed to confirm this. If such a record is played backwards, and then turned around again in software, the wear noise should be much reduced. I now have everything needed to do this, but have yet to reverse the soundstream and listen to the result. Listening to the reversed sound seemed disappointing, but the jury will be out until I re-reverse the sound and listen to several worn records.