Forgot to "return" from i combinator.

thun/asm-dump.txt

@@ -184,6 +184,7 @@ label(H1),
 lsl_imm(6, 6, 15),
 ior(6, 6, 7),
 store_word(6, 0, 0),
+do_offset(H),
 label(I1),
 expr_cell(R, 4),
 expr_cell(S, 0)].

thun/compiler.markII.pl

@@ -158,6 +158,7 @@ Mark II
     sub_base_from_offset(TEMP0, SP),
     sub_base_from_offset(TEMP1, SP),
     merge_and_store(TEMP0, TEMP1, SP),
+    jump(Main),  % We already wrote the stack cell so 'Main' not 'Done'.
 
 
     % ======================================