I found that this happnes to me, when I got a sset from a an api function, as for example, in "tpm_elemss".
This function, returns a sset, but it is not released when settting this sset to nil.
The solution I found, was to write an arx function in C, that relesae the sset.
It seems that tpm_elemss, it is writeen in 'C', and must be release with the 'acedSSFree(ss)' function as well.
Based on this, I suppoused that each autodesk api function that returns a sset, must be trated the same way