copy of an older, barely legible manuscript?

[Bluetoes101]

I'm sorry, but I don't really understand your answer in this context. Could you clarify that again?

If you were unsure/working out, new vellum would be a very strange choice. I'm not sure there's other examples of this.
If we are to take LFD "many scribes" work as correct, it's hard to see a group of people doing this rather than using a chalkboard and talking about the possible/correct interpretation or something along those lines. 

So, those points make the idea possible but unlikely. The following, imo, takes it from unlikely to incorrect. 

If the idea is that people were unsure about if a glyph was o, qo or y etc, we wouldn't see the positional variance (or lack of) with these glyphs.
You would expect to see words that end in qo and o with great frequency as they didn't know if it was o, y or qo, but we don't, they are mostly just y.
This is just one small example and the further this idea is expanded the clearer the issue will be.

There is, imo, repetition and almost-repetition (slight variants) that happen on a line, and also vertically but some examples are so vast that almost an entire page would need to be dedicated to one unsure line. 
If we are to consider that, then also the same words repeat, so were they unsure then sure again then unsure again? Why are surrounding words entirely different?
Some examples can look like unsure variance, but if you took something like the below it becomes pretty difficult to attribute it to that even though I cherry picked an example with lots of almost-repetition