Hiya,
Those pins are NOT meant to take any weight !!
They are just meant to align the seat when the clamps are loose - then the clamps should be tightened (as tight as you can). the clamps take the load … which is why they MUST be tight … or load will be transfered to pin, and that will break !
The pins only cost a few cents, I would imagine your dealer will send one out for free, if you ask nicely 
The old one can be removed by carefully unscrewing it from below with pliers / grips. (or if that fails is a dremel to make a screw driver slot).
For more info see the service site …
strida.nl/english/service.ph … ge=manuals includes manual
and
Tips…
strida.us/Tips-from-Mark.pdf
good luck and enjoy your flying triangle