Tenuto AND ties get removed when only one selected

I have a piece where I wanted to emphasize that three groups of tied notes were to be played full value. I selected the three groups which were on the same screen as they were very close together and clicked the tenuto icon and the marks appeared but on all notes in the groups. I did not like the way that looked so I wanted to remove those marks and use the word tenuto instead. The tenuto notes and the ties were very close together.

I selected one tenuto mark, right clicked and selected "select all on same stave" and pressed delete.

Sure enough the tenuto marks deleted but so did many, but not all of the ties on the same staff, which I didn't notice at the time.

So I had to go through all that staff to replace the ties.

Why were the ties removed as well as the tenuto markings?