Quoted from Texasff78:
I've reached out to Stern by email but have not heard back yet.
I suppose it's possible "playfields aren't made like they used to" or whatever argument you want about softer woods, etc. There are two explanations and they're not mutually exclusive: the playfields are different materially, or the game is different. The major cause, I believe, is the latter. Most modern games seem to play much faster, more prone to airballs as a result, have more multiballs on average, more targets/stuff to do. The result is more dimpling.
Perhaps better QC and engineering would help. But even if the playfield is solid oak, it will still dimple if the gameplay is frantic. I did a quick test -- excuse the poor quality. I have a solid door that I use as a work bench -- I thought it was oak, but I'm not sure and I've had it 30 years; it weighs a ton. I dropped a pinball from 3 inches. You can see the dimple. I'm not saying this explains everything, but I've come to accept that playing pinball is like being a car collector living on gravel roads. If you drive them, they're going to get dinged up.
Edit: one last thing -- I think 'auto playing' pinball machines are great to test overall resiliency. But this might not simulate real world gameplay that would result in more airballs, multiballs, etc.