CAS memory corruption (6975)

[Snorre]

Hello,

while playing a bit with the CAS I often end up with a corrupted memory. Finally I've managed to construct a simple case which reproduces this error quite reliable:
       
When evaluating my Z-Transformation ZT(f,z) for the first time (which gives the expected result) the memory corruption occurs. After that, the CAS behaves quite strange: cannot find defined variables, odd-named matrix variables, sometimes two variables with the same name, eventually not even able to do a clean restart (so have to delete CAS-vars manually). The more I proceed to play with the CAS the worse it becomes.

It doesn't seem to be related to using the same variable names in different contexts, since I end with a corrupted memory too if using distinct names in every place, e.g. g(k):=c^k. Furthermore the quirky outcome differs sometimes when repeating these steps.
Maybe there's a bug within the internal clean-up routines when leaving a local scope, but I don't know...