Some audio files being converted to elastic...against my wishes

Hi all,

I'm struggling with importing. I exported all of my tracks from Studio One to bring into Pro Tools and most are just fine. However, whenever I import one of two mono tracks (bass top and bass bottom) Pro Tools immediately creates a poly version of the file and nothing lines up correctly.

None of my other tracks appear to have this issue, and I've disabled the elastic setting in the options.

I've tried creating new tracks in case it was tied to the event track, and I've re-exported the files. Nothing is working.

I'm hoping someone here can help.

James