Essentially if the examiner thinks an exercise has not been completed to the standard required then the option of a repeat is possible however:
Repeats are not a right, they are at the discretion of the examiner
They should be granted at the end only to allow the whole check to be assessed. Should the performance be deemed to require further training or checking then no repeat should be granted.
Multiple repeats are not recommended as it would indicate further training or checking.
An exceedance will be noted however should you deviate and correct immediately there is likely to be no repercussions however a significant error will result in a repeat/partial pass.