I agree.
I think this might have been an issue during the production of the playfield. Not enough primer to "bite" into the wood. The sun may have dried the section up and as a result, it has split the paint creating the cracks in the playfield. not a common problem, but I've seen what appears to be this issue only a handful of times.
Trust me to get the one that does this. My reasonably hard playfield fixerup has now become a damn sight harder. This pinball has been teaching me one thing and that is patience!
This is one of the "trying moments" in pinball restoration. I've seen sections the size of 20 cent pieces fly off the playfield while simply using an air compressor to blow the dust off. What you are dealing with is a very thin layer of primer, just enough paint to cover the section and a thin layer of varnish. This has been slowly worn away over 40 years. The machine was only meant to last 5-10 years, so it is amazing that they are still around !
Patience - Yes - In spades !
