Whether this is acceptable or not to people is a personal thing, but one thing it is not is isolated. This is a common playfield finish that is not considered an error or a reason to send back a new machine. Many thousands of machines have PFs like this. Sure, avoid it if you want when buying used, but expect it in one out of every four at least new machines, and it has been like that for years.

Ribbing is not an “issue”. It has been turned “into” an issue. It’s got nothing to do with quality control in the same way that ghosting or cracking clear do. It’s a statistical variation.

Now, it might become a “preference”, but it is not an “issue”. When you buy a machine I can imagine a situation in which you ask for one that has no ribbing in the playfield, but it’s not something that has to be eliminated.