BibTeX does not have the right entry for preprints. This is a hack for producing the correct reference:
@booklet{EasyChair:9790,
author = {Julia Werneth and Christian von Deimling and Michael Eßig},
title = {Innovation Contests in Public Procurement: Challenges as a New Instrument?},
howpublished = {EasyChair Preprint 9790},
year = {EasyChair, 2023}}