Problem with sewing tackle twill kiss cut and thread

[Carol1950]

I am sewing tackle twill split chest designs on Under Armor vests which have very thick seams going down the middle on either side of the buttons.  When the machine tries to sew the kiss cut twill over the top of these seams, the thread won't go down or stay down and stay connected with the bobbin thread.  This leaves patches of no stitching on the twill which means I have to stop the embroidery machine, back up and try again and again and again until it finally decides to catch a stitch or two.  I have even tried sewing 2 stitches at a time, stopping it, and doing 2 more, etc.  It is driving me CRAZY!!!  Anybody got any hints for this???  Hirsch was no help. They said try a titanium needle, which I did, but it is still doing it.  I am using the traditional zig zag stitch.  Help!