Yamaha DTXpress/DTXplorer/DTXtreme

Hi, I was wondering if someone could help me.  I have the original 
DTXpress and I'm trying to set up a bassline to play in chase mode from 
a single pad. I have recorded it into the module onto track 1 and if I 
play it back it works fine however if I assing it to a pad and set it 
to chase mode it will only play the first 9 notes and then the 
remaining notes will struggle to come out.  If I select one of the 
preset songs and set it to chase mode it will play correctly even 
though there are more than 9 different bars.
Is there something I'm doing wrong?

Please help.

Z