Barudan hanging help

we have a 15 head old '98 barudan. i set the machine up to run out a logo, that i've ran out several times before on this machine, on all 15 heads. i got about a 1/3 into the logo when it sounded like the machine hung up for less than a second as it continued sewing. this threw the design out of register. i stopped it and tried to figure out where the hang up was at. basically i found that i could run 4 or less hats out without it hanging up on any of the heads at a time. 5 or more hats, on any of the heads, and it would hang up. i've got a job of over 250 hats to run out. i do not want to run these 4 at a time.

any ideas on what can be going on? i tried turning the machine off and manually moving the frame to see if there is anything causing it to hang up and found nothing. it moved smoothly.

please help.. i'm at a loss as to what's going on.