Accusations of Deception to “Control” Questions

[underlyingtruth]

From page 115 TLBTLD

Examinees who answer the probable-lie "control" questions dishonestly may be surprised to learn later that they passed. They may come to believe that they got away with lying on their polygraph examinations and lose their fear of the polygraph. This could pose a problem for agencies that subject their employees to repeated polygraph screenings.

I wonder at what point a polygrapher would consider someone's experiences with the polygraph and knowledge of the testing procedure to be too affected to permit them to be a viable candidate for the test.
Even if one were to never visit this site, or obtain information about the workings of the polygraph, if they are repeatedly tested over years, they will begin to notice patterns in the testing procedure that would cause them to doubt the validity of the test.  As quoted above, if an honest person believes that they lied to a control question (not knowing that it is a CQ), they very well would conclude that they "beat" the test or at least begin to doubt the validity of the results.
The exact opposite would begin to occur (as it did with me) with someone who repeatedly fails exams knowing that they were as honest as one could humanly be.
This indeed seems like it could be a problem for agencies that regularly test or for programs (treatment or probation) that rely so strongly on polygraph exams.

Has anybody had the experience of disclosing their understanding of the polygraph to an examiner and thus been denied the test?  
Would a polygrapher refuse to test a fellow polygrapher for a criminal investigation?

George, I am having trouble connecting the last the last line in that section

By accusing an examinee of "having trouble" with regard to the "control" questions, such persons may be led to believe that there really is something to polygraph "testing."

with the paragraph above.  Was this a continuation of the same thought or an alternative possibility?

[George W. Maschke]

The passage you cited proposes an alternative reason why a polygrapher might accuse a subject of deception with regard to a "control" question. The latter sentence you quoted is a direct continuation of the train of thought of the former (hence its inclusion in the same paragraph).