A system has a static call to a frozen external procedure.  After initial 
compilation where the system is frozen, system execution works
correctly.  Then a postcondition is added to the external
procedure.  After the compiler correctly detects the VSTA(2)
error, the postcondition is removed and compilation finishes.  But
system execution then evaluates the removed postcondition.

Discovered in release 5.4.0722.