Omg I soooo stupid... I know exactly why you can´t replicate my issue, because there is none. It was all a huge misunderstanding on my part.
Back when I purchased the plugin it was on version 2.69. I set it up and it was perfect for my needs, because a dual wielding char with 2 weapons in his hands was attacking only ONE time. That was exactly the behavior I was looking for. I just wanted one damage pop-up regardless if the char is one-handed, two-handed weapon or has two weapons in his hands.
Time went by and I was working on other parts on my game where the dual wielding character was not important and I think I never tested it again. Now that wrong behavior from version 2.69 is fixed and my brain thinks it´s wrong... there is a bug.. and so on... Completely blind by the fact that this was never an intended feature...
To finalize my post of stupidity I would like to suggest such a feature. An option to not attack twice, even if the character is holding two weapons.
Sorry for the confusion I have caused!