Big PL/SQL block passes wrong parameters for function call

During executing a big PL/SQL blocks, some of the numeric parameters get lost/replaced with an earlier value. There is no error message, the PL/SQL block executes, but some of the function calls get the wrong parameter values. See the LiveSQL link: it defines a function which compares its input parameters, and calls it some 11 thousand times, and at the 10932th call, it gets mismatched values. The problem seemingly occurs above a certain program size, but it seemingly didn't reach the diana nodes limit, there is no ORA-00123, the program executes, but stores the wrong data in the database. Is there a size limit I bump into or can it possibly be an Oracle bug (that reproduces on multiple instances and different Oracle versions?)