BibTeX does not have the right entry for preprints. This is a hack for producing the correct reference:
@Booklet{EasyChair:5259,
author = {Gan Chun Seng and Samer Saed Saheel Wahdain and Amir Izzani Mohamed and Mona Riza Mohd Esa and Zulkarnain Bin Ahmad Noorden},
title = {Lightning Attachment to Wind Turbine Blades},
howpublished = {EasyChair Preprint no. 5259},
year = {EasyChair, 2021}}