Update: indeed was because nfs was forced to work with VideoPlayer. I don't have to manually add mkv in rule filetypes.
So one question for Himedia/Futeko: Is there a reason to redirect all nfs connections to VideoPlayer?
Follow-up: is there a preferred way to add shares from 2 different NASs, each with its own user/pass and play movies with Wrapper (aka if I add network locations from Kodi interface, are the credentials passed to Wrapper?). I don't want to install any patch to achieve this. I tend to keep the configuration as default as possible to be able to run into a working state as soon as any upgrade is performed - and that not only for my Q10Pro, is a habit I have to customize things as little as possible in order to preserve the compatibility after software upgrades.