Trouble With Ties

I'm arranging a piece for an upcoming audition. I'm trying to add some ties to the score but when I select the notes I want to tie (or select the measure, I've tried both) instead of tieing the notes I selected it ties each of them to the next note of the same pitch. I've included screenshots showing what I mean. I'm trying to tie C A F together, all in the same measure, but instead it's tieing the C to the next C that appears in the score, A to the next A that appears in the score, etc etc...

I can drag the tie over to the note I want it to be on but then it doesn't play correctly, which isn't a big deal when I'm reading it but I'd like it to actually work properly if I decide to upload my arrangement. Does anyone know what's going on or how to fix it?