range selection not functioning but only in sessions using certain samples

I am trying to slice some beats out of a pre-existing sample set and am unable to select ranges in either range mode or smart object mode. It works fine in other sessions. The only possibility I can see is the samples are 16-bit .wav and the sessions are 32-bit.

I am using Ardour 4.4.0 on a ubuntu studio 14.04 set up.

Any thoughts?

You’ve provided no description of what actually happens. That would be a first step.