Hello,
I have a finished script where I use (z). I once feed it a data:

^FZUI^_ text-field example:
^Zzuitfieldtfield1_1^Z''^Z''^Z1^ZZUI\[my_tfield1_width\]^ZZUI\[my_tfield1_start\]^ZZUI\[my_tfield1_data\]^\

on which for 4th "^Z..." segment it was returning multiple segments.
This happened for 5 minutes, then it stopped. Because I wasn't touching
the script-black-box, I think it's really a (z) thing. I suspect some
missing "calloc" instead of "malloc", etc. So maybe it's worth adding
this test case (patch attached) to D04parameter with this exact data:

  foo="^FZUI^_ text-field example:
  ^Zzuitfieldtfield1_1^Z''^Z''^Z1^ZZUI\[my_tfield1_width\]^ZZUI\[my_tfield1_start\]^ZZUI\[my_tfield1_data\]^\"
  print "${#${(z@)foo}}"
0:Test real-world data that once seemed to fail
>4

-- 
  Sebastian Gniazdowski
  psprint3@fastmail.com