This happens to me, ALL THE TIME.
I write something down on my next actions list.
"Reconfigure server XYZ"
Then I gear up to start, and I realize that either 1) it requires some kind of lengthy setup that could be two or more actions, or 2) I need some input from someone before I can complete the action.
For example, when I went to reconfigure XYZ, I realized I no longer had access to it and I needed to wait for access or ask someone else to do it.
It happens everywhere. Last week I went to an appointment, and realized I absolutely had to get gasoline or I was going to run out. But was "get gasoline" on my errands list? No.
It seems like these "expanding actions" slow me down tremendously. Sometimes I will cross the action off my list and re-write the "in betweens" on my Next Actions or Waiting For list. But it's a lot of re-tweaking, re-writing, re-doing.
Does anyone else encounter this? Is it poor planning on my part, or just the way things are?