When writing, St Thomas would usually dictate to his secretaries. It's an established fact that he could dictate to two or even three secretaries at the same time. He had an amazing capacity for such work.
But I think he too probably had his bad days at the office. Recently I came across something in the Summa that I found humorous.
In answering the question "Can angels work miracles?" Thomas says no, they cannot, because such power belongs only to God.
In responding to the objection that St Gregory said some angelic spirits can work wonders, Thomas replies that they could be said to work miracles only in the sense that either God works miracles at their request, or because they act in a ministerial role with respect to the miracles that occur. Then he gives the example that I find humorous: "for example, collecting the dust (of the dead) at the General Resurrecction or doing something of that sort."
For me it conjured up a funny picture of angels going around with little baskets collecting dust and trying to reassemble it into bodies. I don't know how the general resurrection will work, but however God does it through his power, I don't think it would mean physically putting dust back together. So maybe Thomas just had a hard time coming up with a good example, especially if he was dictating to more than one secretary, which explains his further comment, "or doing something of that sort."