Mutation of function input parameter

Hi all.

I am not sure if the following is question for forum, but I have strange behavior of function's input parameter with name "which".

I am using Virtuoso IC6.1.8-64b.500.17

In the following function input parameter with name "which" is getting changed from time to time.

I caught mutation with printline-s which are here removed to make function shorter.

Code:

Function is always called with value "Vg" for input parameter "which", but after line

values0 = cadr(cj0)

from time to time it is getting altered.

Any help would be of great value.

Best regards,

Dragan