Email from Jan Meved on 23rd August:

when an RPC output contains a list, and there are n elements in the list, the 1st invocation of the RPC will have the n elements. The 2nd invocation will show 2n elements (all elements listed 2x), the third will show 3n elements (all elements listed 3x), etc. What is needed is replacing the list with each new invocation of the RPC - right now it seems to be appending the elements.