- It looks like ムシレ means小さな欠損 according to the website below.

- 欠損 means damage so I would say it means a “small damage” or “tiny flaw.”

Here is a website on “troubles”
http://www.sakagami-ltd.co.jp/technical/trouble/index.html

小さな欠損（ムシレ）


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Note added at 25 mins (2010-12-23 15:00:36 GMT)
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I would imagine that in the manufacturing of screws, some come out with a small flaw or flaws, small imperfection or imperfections or small damage(s).

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Note added at 35 mins (2010-12-23 15:10:58 GMT)
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I also found the below, which is a past Kudoz answer on the subject of automobiles...
According to the answer, "mushire" is a damage on the surface....
So, for a screw, it must be a small imperfection on the surface of the screw...
I would surmise that the inspection checklist in your translation is about checking whether the screw has such damage or not.

Please see below:
http://www.proz.com/kudoz/japanese_to_english/automotive_car...
ムシレ is damaged condition of part surface, which is caused when a portion of part surface is worn or plucked out.
It also refers to scratch or deterioration.