Sorry about the delay - not sure how this slipped by.
I suspect your stuttering is caused by transcoding - I haven't a Qnap TS259 Pro NAS, but I do know a lot of NAS's do not have the processing power to do any heavy duty transcoding (limited to remuxing only). The Panasonic BD player profile you are using will remux the video and transcode the audio. The confusing part is that the Panasonic 2013 profile should play your file natively (ie. without transcoding).
Can you confirm your file is being transcoded (turn on
detailed logging and play the file - the log file will tell you if transcoded or played natively).
I notice this file has subtitles. What are your settings in Serviio console (Delivery, Subtitles tab). Try both profiles with only the top checkbox selected.