need help please with machine

hi

i have aquired a 6 head happy embroidery machine. on normal embroidery it runs beautiful. however when doing 3d embroidery it just goes haywire. for example the problem i have:

when trimming starts, the bobbin thread goes short, and when it continues in another part of the design the thread comes out of the needle.

the thread starts to fray aswell.

it also breaks in the corner of the design to, it never breaks in the middle just at the corners.

is there anyone who can point me in the right direction as i have so many 3d orders lined up however want the machine to run first before i go ahead. please advice

thanks

dean