Are you preparing your samples on a computer? Because the OT defaults to boosting all samples by 12db (to compensate for the -12db pad it applies when recording) so if you load normalized samples they’ll be much louder than the inputs. You can change that in the attributes page of the audio editor per-sample, but if you work in 24 bit there’s really never any reason for a ample to be anywhere near full scale, peaking somewhere between -12db and -6db (preferrably on the quieter end of that) is good for tracking in a DAW but even that might be a little on the loud side for the Octatrack depending on context.
If your samples are drowning out the input and you aren’t recording them directly on the Octatrack, change their gain from +12 to 0 in the AED and see if that helps.