nailed the bug: what was happening was the labels generated by parse.rkt and parse-bytecode-5.1.1 were colliding, since they were using separate gensym functions.

compiler.rkt

@@ -730,7 +730,8 @@
      (append-instruction-sequences
       ;; Make some temporary space for the lambdas
       (make-instruction-sequence
-       `(,(make-PushEnvironment n #f)))
+       `(,(make-Comment "scratch space for case-lambda")
+         ,(make-PushEnvironment n #f)))
       
       ;; Compile each of the lambdas
       (apply append-instruction-sequences
@@ -1011,9 +1012,12 @@
                                                       'val))))])    
     (append-instruction-sequences
      (make-instruction-sequence 
-      `(,(make-PushEnvironment (length (App-operands exp)) #f)))
+      `(,(make-Comment "scratch space for general application")
+        ,(make-PushEnvironment (length (App-operands exp)) #f)))
      proc-code
      (juggle-operands operand-codes)
+     (make-instruction-sequence
+      `(,(make-DebugPrint (make-Reg 'proc))))
      (make-instruction-sequence `(,(make-AssignImmediateStatement 
                                     'argcount
                                     (make-Const (length (App-operands exp))))))
@@ -1313,7 +1317,8 @@
                                                         (make-EnvLexicalReference i #f)
                                                         'val))))])    
       (append-instruction-sequences
-       (make-instruction-sequence `(,(make-PushEnvironment (length (App-operands exp)) #f)))           
+       (make-instruction-sequence `(,(make-Comment "scratch space for statically known lambda application")
+                                    ,(make-PushEnvironment (length (App-operands exp)) #f)))           
        proc-code
        (juggle-operands operand-codes)
        arity-check
@@ -1688,7 +1693,8 @@
           linkage
           extended-cenv
           (append-instruction-sequences
-           (make-instruction-sequence `(,(make-PushEnvironment 1 #f)))
+           (make-instruction-sequence `(,(make-Comment "scratch space for let1")
+                                        ,(make-PushEnvironment 1 #f)))
            rhs-code
            body-code
            after-body-code
@@ -1728,7 +1734,8 @@
           extended-cenv
           (append-instruction-sequences 
            (make-instruction-sequence 
-            `(,(make-PushEnvironment n (LetVoid-boxes? exp))))
+            `(,(make-Comment "scratch space for let-void")
+              ,(make-PushEnvironment n (LetVoid-boxes? exp))))
            body-code
            after-body-code
            (make-instruction-sequence 
@@ -1790,7 +1797,8 @@
                   (map (lambda: ([lam : Lam]
                                  [i : Natural])
                                 (make-instruction-sequence 
-                                 `(,(make-PerformStatement 
+                                 `(,(make-Comment (format "Installing shell for ~s\n" (Lam-name lam)))
+                                   ,(make-PerformStatement 
                                      (make-FixClosureShellMap! i (Lam-closure-map lam))))))
                        
                        (LetRec-procs exp)

lam-entry-gensym.rkt

@@ -0,0 +1,14 @@
+#lang typed/racket/base
+
+
+(define-values (make-lam-label reset-lam-label-counter!/unit-testing)
+  (let ([n 0])
+    (values
+     (lambda ()
+       (set! n (add1 n))
+       (string->symbol (format "lamEntry~a" n)))
+     (lambda ()
+       (set! n 0)))))
+
+
+(provide make-lam-label reset-lam-label-counter!/unit-testing)

parse-bytecode-5.1.1.rkt

@@ -5,6 +5,7 @@
          "typed-module-path.rkt"
          "path-rewriter.rkt"
          "parameters.rkt"
+         "lam-entry-gensym.rkt"
          syntax/modresolve)
 
 
@@ -386,15 +387,6 @@
   (make-Splice (map parse-item body))))
 
 
-(define-values (make-lam-label reset-lam-label-counter!/unit-testing)
-  (let ([n 0])
-    (values
-     (lambda ()
-       (set! n (add1 n))
-       (string->symbol (format "lamEntry~a" n)))
-     (lambda ()
-       (set! n 0)))))
-  
 
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

parse.rkt

@@ -5,12 +5,11 @@
          "lexical-structs.rkt"
          "helpers.rkt"
          "parameters.rkt"
+         "lam-entry-gensym.rkt"
          racket/list)
 
-(provide (rename-out (-parse parse))
-         
-         ;; meant for tests
-         set-private-lam-label-counter!)
+(provide (rename-out (-parse parse)))
+
 
 (define (-parse exp)
   (let* ([prefix (construct-the-prefix exp)])
@@ -205,28 +204,21 @@
                        #t
                        lam-body
                        (map env-reference-depth closure-references)
-                       (fresh-lam-label))]
+                       (make-lam-label))]
             [else
              (make-Lam (current-defined-name)
                        (length (lambda-parameters exp))
                        #f
                        lam-body
                        (map env-reference-depth closure-references)
-                       (fresh-lam-label))]))))
+                       (make-lam-label))]))))
 
 
-(define lam-label-counter 0)
-(define (set-private-lam-label-counter! x)
-  (set! lam-label-counter x))
-(define fresh-lam-label
-    (lambda ()
-      (set! lam-label-counter (add1 lam-label-counter))
-      (string->symbol (format "lamEntry~a" lam-label-counter))))
 
 
 
 (define (parse-case-lambda exp cenv)
-  (let* ([entry-label (fresh-lam-label)]
+  (let* ([entry-label (make-lam-label)]
          [parsed-lams (map (lambda (lam)
                              (parse-lambda lam cenv))
                            (case-lambda-clauses exp))])

test-parse.rkt

@@ -3,6 +3,7 @@
 (require "parse.rkt"
          "lexical-structs.rkt"
          "expression-structs.rkt"
+         "lam-entry-gensym.rkt"
          (for-syntax racket/base))
 
 ; Test out the compiler, using the simulator.
@@ -13,7 +14,7 @@
        (syntax/loc #'stx
          (begin
            (printf "Running ~s ...\n" (syntax->datum #'expr))
-           (set-private-lam-label-counter! 0)
+           (reset-lam-label-counter!/unit-testing)
            (let ([expected expt]
                  [actual 
                   (with-handlers ([void