This is a minimal LEF to reproduce the problem. I'm not sure how to upload an attachment or I would provide a more complete test case. Thanks.
VERSION 5.6 ;
UNITS
DATABASE MICRONS 2000 ;
END UNITS
PROPERTYDEFINITIONS
VIA OR_DEFAULT STRING…
I will put one together but it is just inside a VIA statement in LEF. Btw, why write your own parser when Si2 provides an open source parser (https://si2.org/oa-tools-utils-libs/)