KnitBot

I believe I finally cracked the mystery of getting my Brother KH930 to
knit lace properly.  I’d struggled with this before, to no avail.

Brother knitting machines have a separate lace carriage that is used to
transfer stitches.  That is, you use the regular carriage to knit
some fabric, switch to the lace carriage to transfer stitches from one
needle to another.  This is what creates the equivalent of “knit
together” and (on the next knit row) yarn over.  It can take
several passes, depending on which way the stitches are meant to lean.
  The electronic program you’ve selected controls which stitches
get slipped where.   And, once they are all set up, you go back to
the regular carriage and knit a row, two or more.

Simple, yes?  And — fraught with peril.  Lifting stitches
off a needle is rarely a challenge for the lace carriage. 
Depositing them on the appropriate other needle is sometimes less
successful.  My experience was that I’d get along mostly okay and
then the machine would drop one stitch in 10.  Well, that’s A
LOT!    More than you can reasonably keep an eye on to
fix if you notice a stitch that looks like it’s about to take a suicide
dive on the next pass.  And it just made a nasty tangle instead of
lace.

I looked at any number of things — more weight on the bar pulling the
fabric; less tension; more tension; bent needles… no use.

The following swatch was worked bottom to top.  You can see things
started out poorly (though this is hardly the worst example).  And
then I Figured It Out, and things worked almost perfectly.

I suppose I should work a few more efforts before declaring absolute
victory, but here’s the key thing that seemed to make a (logical)
difference:  I ran the fabric being knit down over the ribber
needles (i.e., I covered the ribber needles with a piece of cardboard,
and kept the knitting in the front of the machine instead of having it
drop down between the ribber and the main bed.  Put another
way:  remove the angle of the backwards tilt of the main bed
introduced when you attached the ribber.

Or, perhaps most succinct:  use the ribber OR the lace carriage,
but never the 2 at the same time.