A client hired me to research and recommend workstation setups for a group of employees, each of whom had unique needs. They had already purchased some equipment and needed to make sure everything else was compatible.
The client ordered some equipment counter to my recommendations. I then spent time researching what they ordered to make sure it would be compatible before I went on site.
I spent nearly as much time on research and communication as I did on site. I'm looking at my log now and wondering why it took me 30 minutes to draft that email. Per our agreement, all this time is billable and the client will not be surprised, but I really am embarrassed now at how long it took.