Hi Larry,
I assign fillins to my sequenced songs as follows:
First I use Track 4 as a "CHD" track so I can assign all the chords to the song, ahead of time, so I don't have to play them during recording.
To assign a fill-in I go to:
Program Menus
Sequence
Record and Edit
Step Record
Chd - Track 4
I then click on Fill 1 or Fill 2 button and can assign the fill in to any beat in any measure that has a chord assigned (to that beat)
This works best for me with no problems.
Hope this helps.
Larry