fwiw ...
i have 7 or 8 different brand/model string serving servers, plus a few i made from scratch.
in the long run, a simple server like the little spinner ...
... works as good -if not better- than the complicated and expensive ones. a simple serving tool is easy to make, to boot.
i bought the 'high tech' bear paw serving tool and think it's a total waste of money, a real 'bear' to make work well if not at all.
ALL serving tools need fiddling and adjusting and adding washers (and/or springs) of varying materials and thicknesses as adjustable spool drags.
with a new, fully loaded serving thread spool, more tension is required to keep the jig under control when its spun.
and finally, ALL serving tools have a learning curve. have patience, think logically, practice, stay the course and you will be rewarded.