Apparently Skeggi has descendents of Losteriksson so perhaps ineed someone translating just caught a Norse explorer born in Skeggi introducing proud heritage and "yadd yadda Olaf Eriksson yadda yadda Losterikssson [thumps chest] yadd yadda" became "Losteriksson". When really it was "I am Olaf son of Erik, a descendent of Losteriksson".
There's a reference to the explorer recounting discovering in Altdorf.
I don't know WFRP Norse naming conventions but in some Norse conventions there weren't actually family names just "son of", "daughter of". So "Losterikkson" would not be a family name in that case.