"Scribes Avoiding Imperfections in Their Writing Matierials" Archiv für Papyrusforschung 61.2 (2015): 371-383.Dr. Jones discussed several phenomenon of imperfections that a scribe may encounter while performing their task; cracks, folds, tears, holes, separated or shrunken fibers, stains, and κολλήσεις (joint seams). The article is summarized nicely on his blog, here.
In short, if a scribe encountered a feature on the page they were inscribing, the copyist would more than likely have to pull the pen away from the page and then place it back in a (sometimes drastically) different location. For example, in the case of a hole, the scribe would have to alter the placement of the letters by writing around the defect in some way. Dr. Jones highlighted this phenomenon on pages 376-378. This occurred in the case of Codex Sinaiticus through-out the manuscript, in particular, on Q84-f.5.r, at the bottom of the first column.
|A Scribe avoiding a hole in the parchment C. Sinaiticus (Q84-f.5.r)|
Dr. Jones also highlights another similar case at Q18-f.6.r on page 377 of his article.
I find this fascinating, especially in its relation to the introduction of scribal errors in the copying of the text. In a particularly bad case in Codex Bezae that Jones highlights on page 377 of his article, the scribe had to avoid a large hole, writing the text around the imperfection.
|A scribe avoiding a hole in C. Bezae (f. 205r)|
Peter M. Head and Mike Warren, "Re-inking the Pen: Evidence from P. Oxy. 657 (P13) Concerning Unintentional Scribal Errors." New Testament Studies 43 (1997): 466-473.In the article, Dr. Head and Dr. Warren contend that,
"the constant necessity to re-ink one's pen provided the opportunity for scribal distraction at the level of eye, memory, judgement and pen, and would thus have been an occasion for the introduction of unintentional copying error." (pg. 466)This may (must) be true in the case of defects in the writing material. The lifting of the pen and the distraction of avoiding the imperfection may have led to the introduction of an error in the copying of the text.