It says in the Linguistics skill that you can retry it. I can't see how this works... if I came across Arabic writing, and I didn't know what it said (say I made a low roll), I wouldn't be able to just figure it out by looking at it for another minute. I would understand if it was "Retry: Yes, if you can do further research on the language," or something similar. How do the rules justify someone just figuring out the meaning of writings in a language they haven't seen before half the time by just sitting there for twenty minutes?
Player: I sit there and retry again, and again, and again, and again, and again, and again. OK... let's see, I think it says this or this. One of these is a false conclusion, since they don't match. I have a 50% chance to understand ANY writing I come across.
If you go by what it says it says that success lets you figure out the "general concept". Of the piece, not necessarily exactly what it say. So you might be able to say that it was some sort of instructions for building a device, but not be able to get enough detail to precisely follow them. I suppose a lot depends on what you define as 'general content'.
I think they just failed to properly explain.
I don't think you can retry understanding the text if you fail to understand it the first time and then fail the wisdom check to know you fail. Because as a player you shouldn't actually know you failed both.
If you know you failed the check to understand the document by making the wisdom check sucessfully then I would say it's reasonable to spend more time trying to accurately decipher it. It's like when people starting trying to decipher the Dead Sea scrolls. They didn't just look at it and start reading, they spent a long time and using a key eventually decoded what it said. I would simulate this by allowing a take 20 if the had access to some relevant research documents and spent some days or hours doing the research and interpretation.
However, none of this is really spelled out in the rules.
I think the retry part is honestly misleading because I'm not sure what it refers to.