I remember this being a tight squeeze. I think it was simply a little burr on the hole. You can try some sandpaper or a deburring bit.. or maybe even just an awl. Worse case is you can use a drill bit to open the hole a small amount.
Rob Carsey, North Brunswick NJ
RV-12iS (N713) / Completed 12/2020
ASEL, Glider, AGI/IGI, LSRM-I, FCC GROL