Longacre, Drew. "Developmental Stage, Scribal Lapse, or Physical Defect? 1QIsaa’s Damaged Exemplar for Isaiah Chapters 34–66." Dead Sea Discoveries 20, no. 1 (2013): 17-50.
The Great Isaiah Scroll from Qumran (1QIsaa) does not generally reflect a text form earlier than the Masoretic text. Instead, the convergence in 1QIsaa of patterns of spacing irregularities, literary and textual problems, and secondary supplementations, as well as a consistent pattern of distribution, are best explained on the basis of the hypothesis of an exemplar for chapters 34-66 with a damaged bottom edge. Upon reaching the defective edge in each column of his exemplar, the scribe dealt with any lacunose or illegible text in one of two ways before continuing with the unaffected text at the top of the subsequent exemplar column. Sometimes he left blank spaces in his new copy to be filled in with the correct text from other manuscripts at a later time. At other times he attempted full or partial reconstructions of the text based on whatever text remained legible in the damaged exemplar, memory, and contextual clues.
I previously blogged about this here.