I remember testing 12SP18 and seeing duplicate stuff. Duplicate TOC entries (especially TOC Views), duplicate columns ,... . But this was mainly CUI related, cause 12SP18 contains a few code optimizations for the upcoming TOC editor.
What events are used for calling your custom Methods? What you describe sounds like a server Method. Is this one called from a client Method? There are circumstances that can call a client Method twice, but I am just guessing.
General speaking: 12SP18 tells me that you have a subscription, why don´t you ask Aras? [emoticon:0f36700dfeb3494fa10d47dd9e1f90a1]This forum is great for general questions, but your topic is really very specific.