buggy

block {
  block { 
    ref x 
    ref x 
    value «proportion» 
    ref x 
    do int_multiply } 
  block { 
    block { 
      ref x 
      do int_add 
      block { 
        do int_add 
        ref x 
        do int_add 
        value «bool» } 
      do bool_not 
      ref x } 
    ref x 
    do int_add 
    ref x 
    block { 
      do bool_and 
      block { 
        do bool_not 
        do int_add 
        do bool_or 
        do int_add 
        value «int» } 
      do int_subtract 
      value «bool» 
      block { 
        do int_greater_than               <= there's the culprit; not sure why it fails this way though
        do int_abs } } } 
  ref x 
  ref x 
  ref x}
  \n«proportion»0.578693542001044\n«bool»false\n«int»-4\n«bool»true

So the immediate cause is the appearance of "int_greater_than" in the code. Still digging upstream to see how that breaks the program, which it shouldn't.